* [PATCH v2 1/1] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: refine flash detection
@ 2023-06-01 6:08 Gerd Hoffmann
2023-06-01 8:22 ` Oliver Steffen
0 siblings, 1 reply; 3+ messages in thread
From: Gerd Hoffmann @ 2023-06-01 6:08 UTC (permalink / raw)
To: devel
Cc: Ard Biesheuvel, Oliver Steffen, Jordan Justen, Pawel Polawski,
Jiewen Yao, Gerd Hoffmann
Flash can be write-protected in qemu (which is usually the case for
code). In case the variable store flash block is configured read-only
ovmf wouldn't be able to store EFI variables there, so not setting up
fvb in that case (and fallhack to emulation) is the better option.
It'll avoid problems later due to flash writes failing.
The patch tries to write back the original value read earlier, so flash
content doesn't change in case the write succeeds. But the status we
read back after the attempt to write will tell us whenever flash is
writable or not.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
index 54f859de9ff9..a577aea55614 100644
--- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
+++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
@@ -114,9 +114,17 @@ QemuFlashDetected (
DEBUG ((DEBUG_INFO, "QemuFlashDetected => FD behaves as RAM\n"));
*Ptr = OriginalUint8;
} else if (ProbeUint8 == CLEARED_ARRAY_STATUS) {
- DEBUG ((DEBUG_INFO, "QemuFlashDetected => FD behaves as FLASH\n"));
- FlashDetected = TRUE;
- *Ptr = READ_ARRAY_CMD;
+ *Ptr = WRITE_BYTE_CMD;
+ *Ptr = OriginalUint8;
+ *Ptr = READ_STATUS_CMD;
+ ProbeUint8 = *Ptr;
+ *Ptr = READ_ARRAY_CMD;
+ if (ProbeUint8 & 0x10 /* programming error */) {
+ DEBUG ((DEBUG_INFO, "QemuFlashDetected => FD behaves as FLASH, write-protected\n"));
+ } else {
+ DEBUG ((DEBUG_INFO, "QemuFlashDetected => FD behaves as FLASH, writable\n"));
+ FlashDetected = TRUE;
+ }
}
}
--
2.40.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH v2 1/1] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: refine flash detection
2023-06-01 6:08 [PATCH v2 1/1] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: refine flash detection Gerd Hoffmann
@ 2023-06-01 8:22 ` Oliver Steffen
2023-06-01 9:07 ` Ard Biesheuvel
0 siblings, 1 reply; 3+ messages in thread
From: Oliver Steffen @ 2023-06-01 8:22 UTC (permalink / raw)
To: Gerd Hoffmann, devel
Cc: Ard Biesheuvel, Jordan Justen, Pawel Polawski, Jiewen Yao
Quoting Gerd Hoffmann (2023-06-01 08:08:03)
> Flash can be write-protected in qemu (which is usually the case for
> code). In case the variable store flash block is configured read-only
> ovmf wouldn't be able to store EFI variables there, so not setting up
> fvb in that case (and fallhack to emulation) is the better option.
I like the term "fallhack", I'll keep that in mind for future use >,<
> It'll avoid problems later due to flash writes failing.
>
> The patch tries to write back the original value read earlier, so flash
> content doesn't change in case the write succeeds. But the status we
> read back after the attempt to write will tell us whenever flash is
> writable or not.
>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
> OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
> index 54f859de9ff9..a577aea55614 100644
> --- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
> +++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
> @@ -114,9 +114,17 @@ QemuFlashDetected (
> DEBUG ((DEBUG_INFO, "QemuFlashDetected => FD behaves as RAM\n"));
> *Ptr = OriginalUint8;
> } else if (ProbeUint8 == CLEARED_ARRAY_STATUS) {
> - DEBUG ((DEBUG_INFO, "QemuFlashDetected => FD behaves as FLASH\n"));
> - FlashDetected = TRUE;
> - *Ptr = READ_ARRAY_CMD;
> + *Ptr = WRITE_BYTE_CMD;
> + *Ptr = OriginalUint8;
> + *Ptr = READ_STATUS_CMD;
> + ProbeUint8 = *Ptr;
> + *Ptr = READ_ARRAY_CMD;
> + if (ProbeUint8 & 0x10 /* programming error */) {
> + DEBUG ((DEBUG_INFO, "QemuFlashDetected => FD behaves as FLASH, write-protected\n"));
> + } else {
> + DEBUG ((DEBUG_INFO, "QemuFlashDetected => FD behaves as FLASH, writable\n"));
> + FlashDetected = TRUE;
> + }
> }
> }
>
> --
> 2.40.1
>
- Oliver
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH v2 1/1] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: refine flash detection
2023-06-01 8:22 ` Oliver Steffen
@ 2023-06-01 9:07 ` Ard Biesheuvel
0 siblings, 0 replies; 3+ messages in thread
From: Ard Biesheuvel @ 2023-06-01 9:07 UTC (permalink / raw)
To: Oliver Steffen
Cc: Gerd Hoffmann, devel, Ard Biesheuvel, Jordan Justen,
Pawel Polawski, Jiewen Yao
On Thu, 1 Jun 2023 at 10:22, Oliver Steffen <osteffen@redhat.com> wrote:
>
> Quoting Gerd Hoffmann (2023-06-01 08:08:03)
> > Flash can be write-protected in qemu (which is usually the case for
> > code). In case the variable store flash block is configured read-only
> > ovmf wouldn't be able to store EFI variables there, so not setting up
> > fvb in that case (and fallhack to emulation) is the better option.
>
> I like the term "fallhack", I'll keep that in mind for future use >,<
>
+1
Merged as #4461
> > It'll avoid problems later due to flash writes failing.
> >
> > The patch tries to write back the original value read earlier, so flash
> > content doesn't change in case the write succeeds. But the status we
> > read back after the attempt to write will tell us whenever flash is
> > writable or not.
> >
> > Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> > ---
> > OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c | 14 +++++++++++---
> > 1 file changed, 11 insertions(+), 3 deletions(-)
> >
> > diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
> > index 54f859de9ff9..a577aea55614 100644
> > --- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
> > +++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
> > @@ -114,9 +114,17 @@ QemuFlashDetected (
> > DEBUG ((DEBUG_INFO, "QemuFlashDetected => FD behaves as RAM\n"));
> > *Ptr = OriginalUint8;
> > } else if (ProbeUint8 == CLEARED_ARRAY_STATUS) {
> > - DEBUG ((DEBUG_INFO, "QemuFlashDetected => FD behaves as FLASH\n"));
> > - FlashDetected = TRUE;
> > - *Ptr = READ_ARRAY_CMD;
> > + *Ptr = WRITE_BYTE_CMD;
> > + *Ptr = OriginalUint8;
> > + *Ptr = READ_STATUS_CMD;
> > + ProbeUint8 = *Ptr;
> > + *Ptr = READ_ARRAY_CMD;
> > + if (ProbeUint8 & 0x10 /* programming error */) {
> > + DEBUG ((DEBUG_INFO, "QemuFlashDetected => FD behaves as FLASH, write-protected\n"));
> > + } else {
> > + DEBUG ((DEBUG_INFO, "QemuFlashDetected => FD behaves as FLASH, writable\n"));
> > + FlashDetected = TRUE;
> > + }
> > }
> > }
> >
> > --
> > 2.40.1
> >
>
> - Oliver
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2023-06-01 6:08 [PATCH v2 1/1] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: refine flash detection Gerd Hoffmann
2023-06-01 8:22 ` Oliver Steffen
2023-06-01 9:07 ` Ard Biesheuvel
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