* Re: [PATCH v2] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: Use physical address with SEV-ES
2021-01-23 13:57 [PATCH v2] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: Use physical address with SEV-ES Lendacky, Thomas
@ 2021-01-23 14:02 ` Lendacky, Thomas
2021-01-25 13:55 ` Lendacky, Thomas
2021-01-26 0:30 ` [edk2-devel] " Laszlo Ersek
2 siblings, 0 replies; 6+ messages in thread
From: Lendacky, Thomas @ 2021-01-23 14:02 UTC (permalink / raw)
To: devel; +Cc: Brijesh Singh, Jordan Justen, Laszlo Ersek, Ard Biesheuvel
On 1/23/21 7:57 AM, Tom Lendacky wrote:
> From: Tom Lendacky <thomas.lendacky@amd.com>
>
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3183
>
> Under SEV-ES, a write to the flash device is done using a direct VMGEXIT
> to perform an MMIO write. The address provided to the MMIO write must be
> the physical address of the MMIO write destitnation. During boot, OVMF
> runs with an identity mapped pagetable structure so that VA == PA and the
> VMGEXIT MMIO write destination is just the virtual address of the flash
> area address being written.
>
> However, when the UEFI SetVitualAddressMap() API is invoked, an identity
> mapped pagetable structure may not be in place and using the virtual
> address for the flash area address is no longer valid. This results in
> writes to the flash not being performed successfully. This can be seen
> by attempting to change the boot order under Linux. The update will
> appear to be performed, based on the output of the command. But rebooting
> the guest will show that the new boot order has not been set.
>
> To remedy this, save the value of the flash base physical address before
> converting the address as part of SetVirtualAddressMap(). The physical
> address can then be calculated by obtaining the offset of the MMIO target
> virtual address relative to the flash base virtual address and adding that
> to the original flash base physical address. The resulting value produces
> a successful MMIO write during runtime services.
>
> Fixes: 437eb3f7a8db7681afe0e6064d3a8edb12abb766
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> > ---
> .../QemuFlashDxe.c | 20 ++++++++++++++++++-
> 1 file changed, 19 insertions(+), 1 deletion(-)
Forgot to add the changelog and use the diffstat options.
The changes address the comments from Laszlo on the v1 version of the patch:
- Update the last paragraph of the commit message
- Limit changes to only the QemuFlashDxe.c file
- Update expression for calculating the physical address
Thanks,
Tom
>
> diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
> index 1b0742967f71..d303b0078b08 100644
> --- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
> +++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
> @@ -16,11 +16,17 @@
>
> #include "QemuFlash.h"
>
> +STATIC EFI_PHYSICAL_ADDRESS mSevEsFlashPhysBase;
> +
> VOID
> QemuFlashConvertPointers (
> VOID
> )
> {
> + if (MemEncryptSevEsIsEnabled ()) {
> + mSevEsFlashPhysBase = (UINTN) mFlashBase;
> + }
> +
> EfiConvertPointer (0x0, (VOID **) &mFlashBase);
> }
>
> @@ -52,11 +58,23 @@ QemuFlashPtrWrite (
> if (MemEncryptSevEsIsEnabled ()) {
> MSR_SEV_ES_GHCB_REGISTER Msr;
> GHCB *Ghcb;
> + EFI_PHYSICAL_ADDRESS PhysAddr;
> BOOLEAN InterruptState;
>
> Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
> Ghcb = Msr.Ghcb;
>
> + //
> + // The MMIO write needs to be to the physical address of the flash pointer.
> + // Since this service is available as part of the EFI runtime services,
> + // account for a non-identity mapped VA after SetVitualAddressMap().
> + //
> + if (mSevEsFlashPhysBase == 0) {
> + PhysAddr = (UINTN) Ptr;
> + } else {
> + PhysAddr = mSevEsFlashPhysBase + (Ptr - mFlashBase);
> + }
> +
> //
> // Writing to flash is emulated by the hypervisor through the use of write
> // protection. This won't work for an SEV-ES guest because the write won't
> @@ -68,7 +86,7 @@ QemuFlashPtrWrite (
> Ghcb->SharedBuffer[0] = Value;
> Ghcb->SaveArea.SwScratch = (UINT64) (UINTN) Ghcb->SharedBuffer;
> VmgSetOffsetValid (Ghcb, GhcbSwScratch);
> - VmgExit (Ghcb, SVM_EXIT_MMIO_WRITE, (UINT64) (UINTN) Ptr, 1);
> + VmgExit (Ghcb, SVM_EXIT_MMIO_WRITE, PhysAddr, 1);
> VmgDone (Ghcb, InterruptState);
> } else {
> *Ptr = Value;
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH v2] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: Use physical address with SEV-ES
2021-01-23 13:57 [PATCH v2] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: Use physical address with SEV-ES Lendacky, Thomas
2021-01-23 14:02 ` Lendacky, Thomas
@ 2021-01-25 13:55 ` Lendacky, Thomas
2021-01-25 22:17 ` Laszlo Ersek
2021-01-26 0:30 ` [edk2-devel] " Laszlo Ersek
2 siblings, 1 reply; 6+ messages in thread
From: Lendacky, Thomas @ 2021-01-25 13:55 UTC (permalink / raw)
To: devel; +Cc: Brijesh Singh, Jordan Justen, Laszlo Ersek, Ard Biesheuvel
On 1/23/21 7:57 AM, Tom Lendacky wrote:
> From: Tom Lendacky <thomas.lendacky@amd.com>
>
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3183
>
> Under SEV-ES, a write to the flash device is done using a direct VMGEXIT
> to perform an MMIO write. The address provided to the MMIO write must be
> the physical address of the MMIO write destitnation. During boot, OVMF
> runs with an identity mapped pagetable structure so that VA == PA and the
> VMGEXIT MMIO write destination is just the virtual address of the flash
> area address being written.
>
> However, when the UEFI SetVitualAddressMap() API is invoked, an identity
s/SetVitualAddressMap/SetVirtualAddressMap/
I can fix that if another version is required, otherwise, can it be fixed
on commit?
Thanks,
Tom
> mapped pagetable structure may not be in place and using the virtual
> address for the flash area address is no longer valid. This results in
> writes to the flash not being performed successfully. This can be seen
> by attempting to change the boot order under Linux. The update will
> appear to be performed, based on the output of the command. But rebooting
> the guest will show that the new boot order has not been set.
>
> To remedy this, save the value of the flash base physical address before
> converting the address as part of SetVirtualAddressMap(). The physical
> address can then be calculated by obtaining the offset of the MMIO target
> virtual address relative to the flash base virtual address and adding that
> to the original flash base physical address. The resulting value produces
> a successful MMIO write during runtime services.
>
> Fixes: 437eb3f7a8db7681afe0e6064d3a8edb12abb766
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
> .../QemuFlashDxe.c | 20 ++++++++++++++++++-
> 1 file changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
> index 1b0742967f71..d303b0078b08 100644
> --- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
> +++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
> @@ -16,11 +16,17 @@
>
> #include "QemuFlash.h"
>
> +STATIC EFI_PHYSICAL_ADDRESS mSevEsFlashPhysBase;
> +
> VOID
> QemuFlashConvertPointers (
> VOID
> )
> {
> + if (MemEncryptSevEsIsEnabled ()) {
> + mSevEsFlashPhysBase = (UINTN) mFlashBase;
> + }
> +
> EfiConvertPointer (0x0, (VOID **) &mFlashBase);
> }
>
> @@ -52,11 +58,23 @@ QemuFlashPtrWrite (
> if (MemEncryptSevEsIsEnabled ()) {
> MSR_SEV_ES_GHCB_REGISTER Msr;
> GHCB *Ghcb;
> + EFI_PHYSICAL_ADDRESS PhysAddr;
> BOOLEAN InterruptState;
>
> Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
> Ghcb = Msr.Ghcb;
>
> + //
> + // The MMIO write needs to be to the physical address of the flash pointer.
> + // Since this service is available as part of the EFI runtime services,
> + // account for a non-identity mapped VA after SetVitualAddressMap().
> + //
> + if (mSevEsFlashPhysBase == 0) {
> + PhysAddr = (UINTN) Ptr;
> + } else {
> + PhysAddr = mSevEsFlashPhysBase + (Ptr - mFlashBase);
> + }
> +
> //
> // Writing to flash is emulated by the hypervisor through the use of write
> // protection. This won't work for an SEV-ES guest because the write won't
> @@ -68,7 +86,7 @@ QemuFlashPtrWrite (
> Ghcb->SharedBuffer[0] = Value;
> Ghcb->SaveArea.SwScratch = (UINT64) (UINTN) Ghcb->SharedBuffer;
> VmgSetOffsetValid (Ghcb, GhcbSwScratch);
> - VmgExit (Ghcb, SVM_EXIT_MMIO_WRITE, (UINT64) (UINTN) Ptr, 1);
> + VmgExit (Ghcb, SVM_EXIT_MMIO_WRITE, PhysAddr, 1);
> VmgDone (Ghcb, InterruptState);
> } else {
> *Ptr = Value;
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH v2] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: Use physical address with SEV-ES
2021-01-25 13:55 ` Lendacky, Thomas
@ 2021-01-25 22:17 ` Laszlo Ersek
2021-01-25 22:35 ` Lendacky, Thomas
0 siblings, 1 reply; 6+ messages in thread
From: Laszlo Ersek @ 2021-01-25 22:17 UTC (permalink / raw)
To: Tom Lendacky, devel; +Cc: Brijesh Singh, Jordan Justen, Ard Biesheuvel
On 01/25/21 14:55, Tom Lendacky wrote:
> On 1/23/21 7:57 AM, Tom Lendacky wrote:
>> From: Tom Lendacky <thomas.lendacky@amd.com>
>>
>> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3183
>>
>> Under SEV-ES, a write to the flash device is done using a direct VMGEXIT
>> to perform an MMIO write. The address provided to the MMIO write must be
>> the physical address of the MMIO write destitnation. During boot, OVMF
>> runs with an identity mapped pagetable structure so that VA == PA and the
>> VMGEXIT MMIO write destination is just the virtual address of the flash
>> area address being written.
>>
>> However, when the UEFI SetVitualAddressMap() API is invoked, an identity
>
> s/SetVitualAddressMap/SetVirtualAddressMap/
>
> I can fix that if another version is required, otherwise, can it be fixed
> on commit?
Yes, I'll fix it on merge. I made the exact same typo in my v1 comment
-- and that was because I copied the mistyped string from the BZ :) (See
c#0, c#1.)
Thanks!
Laszlo
>
> Thanks,
> Tom
>
>> mapped pagetable structure may not be in place and using the virtual
>> address for the flash area address is no longer valid. This results in
>> writes to the flash not being performed successfully. This can be seen
>> by attempting to change the boot order under Linux. The update will
>> appear to be performed, based on the output of the command. But rebooting
>> the guest will show that the new boot order has not been set.
>>
>> To remedy this, save the value of the flash base physical address before
>> converting the address as part of SetVirtualAddressMap(). The physical
>> address can then be calculated by obtaining the offset of the MMIO target
>> virtual address relative to the flash base virtual address and adding that
>> to the original flash base physical address. The resulting value produces
>> a successful MMIO write during runtime services.
>>
>> Fixes: 437eb3f7a8db7681afe0e6064d3a8edb12abb766
>> Cc: Jordan Justen <jordan.l.justen@intel.com>
>> Cc: Laszlo Ersek <lersek@redhat.com>
>> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>> ---
>> .../QemuFlashDxe.c | 20 ++++++++++++++++++-
>> 1 file changed, 19 insertions(+), 1 deletion(-)
>>
>> diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
>> index 1b0742967f71..d303b0078b08 100644
>> --- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
>> +++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
>> @@ -16,11 +16,17 @@
>>
>> #include "QemuFlash.h"
>>
>> +STATIC EFI_PHYSICAL_ADDRESS mSevEsFlashPhysBase;
>> +
>> VOID
>> QemuFlashConvertPointers (
>> VOID
>> )
>> {
>> + if (MemEncryptSevEsIsEnabled ()) {
>> + mSevEsFlashPhysBase = (UINTN) mFlashBase;
>> + }
>> +
>> EfiConvertPointer (0x0, (VOID **) &mFlashBase);
>> }
>>
>> @@ -52,11 +58,23 @@ QemuFlashPtrWrite (
>> if (MemEncryptSevEsIsEnabled ()) {
>> MSR_SEV_ES_GHCB_REGISTER Msr;
>> GHCB *Ghcb;
>> + EFI_PHYSICAL_ADDRESS PhysAddr;
>> BOOLEAN InterruptState;
>>
>> Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
>> Ghcb = Msr.Ghcb;
>>
>> + //
>> + // The MMIO write needs to be to the physical address of the flash pointer.
>> + // Since this service is available as part of the EFI runtime services,
>> + // account for a non-identity mapped VA after SetVitualAddressMap().
>> + //
>> + if (mSevEsFlashPhysBase == 0) {
>> + PhysAddr = (UINTN) Ptr;
>> + } else {
>> + PhysAddr = mSevEsFlashPhysBase + (Ptr - mFlashBase);
>> + }
>> +
>> //
>> // Writing to flash is emulated by the hypervisor through the use of write
>> // protection. This won't work for an SEV-ES guest because the write won't
>> @@ -68,7 +86,7 @@ QemuFlashPtrWrite (
>> Ghcb->SharedBuffer[0] = Value;
>> Ghcb->SaveArea.SwScratch = (UINT64) (UINTN) Ghcb->SharedBuffer;
>> VmgSetOffsetValid (Ghcb, GhcbSwScratch);
>> - VmgExit (Ghcb, SVM_EXIT_MMIO_WRITE, (UINT64) (UINTN) Ptr, 1);
>> + VmgExit (Ghcb, SVM_EXIT_MMIO_WRITE, PhysAddr, 1);
>> VmgDone (Ghcb, InterruptState);
>> } else {
>> *Ptr = Value;
>>
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH v2] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: Use physical address with SEV-ES
2021-01-25 22:17 ` Laszlo Ersek
@ 2021-01-25 22:35 ` Lendacky, Thomas
0 siblings, 0 replies; 6+ messages in thread
From: Lendacky, Thomas @ 2021-01-25 22:35 UTC (permalink / raw)
To: Laszlo Ersek, devel; +Cc: Brijesh Singh, Jordan Justen, Ard Biesheuvel
On 1/25/21 4:17 PM, Laszlo Ersek wrote:
> On 01/25/21 14:55, Tom Lendacky wrote:
>> On 1/23/21 7:57 AM, Tom Lendacky wrote:
>>> From: Tom Lendacky <thomas.lendacky@amd.com>
>>>
>>> BZ: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.tianocore.org%2Fshow_bug.cgi%3Fid%3D3183&data=04%7C01%7Cthomas.lendacky%40amd.com%7Ce7ba4f968a0d4bc42ea108d8c17f0a9b%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637472098694077769%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=jGAzh8XsefGmSnQfjjz%2BQmLJoUu25o67pOxuUORzw7g%3D&reserved=0
>>>
>>> Under SEV-ES, a write to the flash device is done using a direct VMGEXIT
>>> to perform an MMIO write. The address provided to the MMIO write must be
>>> the physical address of the MMIO write destitnation. During boot, OVMF
>>> runs with an identity mapped pagetable structure so that VA == PA and the
>>> VMGEXIT MMIO write destination is just the virtual address of the flash
>>> area address being written.
>>>
>>> However, when the UEFI SetVitualAddressMap() API is invoked, an identity
>>
>> s/SetVitualAddressMap/SetVirtualAddressMap/
>>
>> I can fix that if another version is required, otherwise, can it be fixed
>> on commit?
>
> Yes, I'll fix it on merge. I made the exact same typo in my v1 comment
> -- and that was because I copied the mistyped string from the BZ :) (See
> c#0, c#1.)
Well, looks like I was only able to get it right once... I just noticed
down in the code comment it is wrong, too. Ugh, my fingers just couldn't
type that 'r' I guess.
Thanks,
Tom
>
> Thanks!
> Laszlo
>
>>
>> Thanks,
>> Tom
>>
>>> mapped pagetable structure may not be in place and using the virtual
>>> address for the flash area address is no longer valid. This results in
>>> writes to the flash not being performed successfully. This can be seen
>>> by attempting to change the boot order under Linux. The update will
>>> appear to be performed, based on the output of the command. But rebooting
>>> the guest will show that the new boot order has not been set.
>>>
>>> To remedy this, save the value of the flash base physical address before
>>> converting the address as part of SetVirtualAddressMap(). The physical
>>> address can then be calculated by obtaining the offset of the MMIO target
>>> virtual address relative to the flash base virtual address and adding that
>>> to the original flash base physical address. The resulting value produces
>>> a successful MMIO write during runtime services.
>>>
>>> Fixes: 437eb3f7a8db7681afe0e6064d3a8edb12abb766
>>> Cc: Jordan Justen <jordan.l.justen@intel.com>
>>> Cc: Laszlo Ersek <lersek@redhat.com>
>>> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
>>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>>> ---
>>> .../QemuFlashDxe.c | 20 ++++++++++++++++++-
>>> 1 file changed, 19 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
>>> index 1b0742967f71..d303b0078b08 100644
>>> --- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
>>> +++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
>>> @@ -16,11 +16,17 @@
>>>
>>> #include "QemuFlash.h"
>>>
>>> +STATIC EFI_PHYSICAL_ADDRESS mSevEsFlashPhysBase;
>>> +
>>> VOID
>>> QemuFlashConvertPointers (
>>> VOID
>>> )
>>> {
>>> + if (MemEncryptSevEsIsEnabled ()) {
>>> + mSevEsFlashPhysBase = (UINTN) mFlashBase;
>>> + }
>>> +
>>> EfiConvertPointer (0x0, (VOID **) &mFlashBase);
>>> }
>>>
>>> @@ -52,11 +58,23 @@ QemuFlashPtrWrite (
>>> if (MemEncryptSevEsIsEnabled ()) {
>>> MSR_SEV_ES_GHCB_REGISTER Msr;
>>> GHCB *Ghcb;
>>> + EFI_PHYSICAL_ADDRESS PhysAddr;
>>> BOOLEAN InterruptState;
>>>
>>> Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
>>> Ghcb = Msr.Ghcb;
>>>
>>> + //
>>> + // The MMIO write needs to be to the physical address of the flash pointer.
>>> + // Since this service is available as part of the EFI runtime services,
>>> + // account for a non-identity mapped VA after SetVitualAddressMap().
>>> + //
>>> + if (mSevEsFlashPhysBase == 0) {
>>> + PhysAddr = (UINTN) Ptr;
>>> + } else {
>>> + PhysAddr = mSevEsFlashPhysBase + (Ptr - mFlashBase);
>>> + }
>>> +
>>> //
>>> // Writing to flash is emulated by the hypervisor through the use of write
>>> // protection. This won't work for an SEV-ES guest because the write won't
>>> @@ -68,7 +86,7 @@ QemuFlashPtrWrite (
>>> Ghcb->SharedBuffer[0] = Value;
>>> Ghcb->SaveArea.SwScratch = (UINT64) (UINTN) Ghcb->SharedBuffer;
>>> VmgSetOffsetValid (Ghcb, GhcbSwScratch);
>>> - VmgExit (Ghcb, SVM_EXIT_MMIO_WRITE, (UINT64) (UINTN) Ptr, 1);
>>> + VmgExit (Ghcb, SVM_EXIT_MMIO_WRITE, PhysAddr, 1);
>>> VmgDone (Ghcb, InterruptState);
>>> } else {
>>> *Ptr = Value;
>>>
>>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [edk2-devel] [PATCH v2] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: Use physical address with SEV-ES
2021-01-23 13:57 [PATCH v2] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: Use physical address with SEV-ES Lendacky, Thomas
2021-01-23 14:02 ` Lendacky, Thomas
2021-01-25 13:55 ` Lendacky, Thomas
@ 2021-01-26 0:30 ` Laszlo Ersek
2 siblings, 0 replies; 6+ messages in thread
From: Laszlo Ersek @ 2021-01-26 0:30 UTC (permalink / raw)
To: devel, thomas.lendacky; +Cc: Brijesh Singh, Jordan Justen, Ard Biesheuvel
On 01/23/21 14:57, Lendacky, Thomas wrote:
> From: Tom Lendacky <thomas.lendacky@amd.com>
>
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3183
>
> Under SEV-ES, a write to the flash device is done using a direct VMGEXIT
> to perform an MMIO write. The address provided to the MMIO write must be
> the physical address of the MMIO write destitnation. During boot, OVMF
> runs with an identity mapped pagetable structure so that VA == PA and the
> VMGEXIT MMIO write destination is just the virtual address of the flash
> area address being written.
>
> However, when the UEFI SetVitualAddressMap() API is invoked, an identity
> mapped pagetable structure may not be in place and using the virtual
> address for the flash area address is no longer valid. This results in
> writes to the flash not being performed successfully. This can be seen
> by attempting to change the boot order under Linux. The update will
> appear to be performed, based on the output of the command. But rebooting
> the guest will show that the new boot order has not been set.
>
> To remedy this, save the value of the flash base physical address before
> converting the address as part of SetVirtualAddressMap(). The physical
> address can then be calculated by obtaining the offset of the MMIO target
> virtual address relative to the flash base virtual address and adding that
> to the original flash base physical address. The resulting value produces
> a successful MMIO write during runtime services.
>
> Fixes: 437eb3f7a8db7681afe0e6064d3a8edb12abb766
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
> .../QemuFlashDxe.c | 20 ++++++++++++++++++-
> 1 file changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
> index 1b0742967f71..d303b0078b08 100644
> --- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
> +++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
> @@ -16,11 +16,17 @@
>
> #include "QemuFlash.h"
>
> +STATIC EFI_PHYSICAL_ADDRESS mSevEsFlashPhysBase;
> +
> VOID
> QemuFlashConvertPointers (
> VOID
> )
> {
> + if (MemEncryptSevEsIsEnabled ()) {
> + mSevEsFlashPhysBase = (UINTN) mFlashBase;
> + }
> +
> EfiConvertPointer (0x0, (VOID **) &mFlashBase);
> }
>
> @@ -52,11 +58,23 @@ QemuFlashPtrWrite (
> if (MemEncryptSevEsIsEnabled ()) {
> MSR_SEV_ES_GHCB_REGISTER Msr;
> GHCB *Ghcb;
> + EFI_PHYSICAL_ADDRESS PhysAddr;
> BOOLEAN InterruptState;
>
> Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
> Ghcb = Msr.Ghcb;
>
> + //
> + // The MMIO write needs to be to the physical address of the flash pointer.
> + // Since this service is available as part of the EFI runtime services,
> + // account for a non-identity mapped VA after SetVitualAddressMap().
> + //
> + if (mSevEsFlashPhysBase == 0) {
> + PhysAddr = (UINTN) Ptr;
> + } else {
> + PhysAddr = mSevEsFlashPhysBase + (Ptr - mFlashBase);
> + }
> +
> //
> // Writing to flash is emulated by the hypervisor through the use of write
> // protection. This won't work for an SEV-ES guest because the write won't
> @@ -68,7 +86,7 @@ QemuFlashPtrWrite (
> Ghcb->SharedBuffer[0] = Value;
> Ghcb->SaveArea.SwScratch = (UINT64) (UINTN) Ghcb->SharedBuffer;
> VmgSetOffsetValid (Ghcb, GhcbSwScratch);
> - VmgExit (Ghcb, SVM_EXIT_MMIO_WRITE, (UINT64) (UINTN) Ptr, 1);
> + VmgExit (Ghcb, SVM_EXIT_MMIO_WRITE, PhysAddr, 1);
> VmgDone (Ghcb, InterruptState);
> } else {
> *Ptr = Value;
>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
I've fixed up the typo as discussed elsewhere in this thread, in both
the commit message and the code comment.
Merged as commit 3a3501862f73, via
<https://github.com/tianocore/edk2/pull/1389>.
Thanks
Laszlo
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