Re: [PATCH V4 1/3] UefiCpuPkg/CpuDxe: Add memory attribute setting.

[Anthony PERARD <anthony.perard@citrix.com>]

On Tue, Feb 21, 2017 at 02:57:07PM +0800, Jiewen Yao wrote:
> Add memory attribute setting in CpuArch protocol.
> Previous SetMemoryAttributes() API only supports cache attribute setting.
> 
> This patch updated SetMemoryAttributes() API to support memory attribute
> setting by updating CPU page table.
> 
> Cc: Jeff Fan <jeff.fan@intel.com>
> Cc: Michael Kinney <michael.d.kinney@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Jiewen Yao <jiewen.yao@intel.com>

Hi,

This patch doesn't work on AMD (when running OVMF on Xen). With an AMD
cpu, reading MSR 0x1a0 cause a General Protection Fault.

> +  AsmCpuid (0x80000000, &RegEax, NULL, NULL, NULL);
> +  if (RegEax > 0x80000000) {
> +    AsmCpuid (0x80000001, NULL, NULL, NULL, &RegEdx);
> +    if ((RegEdx & BIT20) != 0) {
> +      // XD supported

This next read is where the fault is taken.

> +      if ((AsmReadMsr64 (0x000001A0) & BIT34) == 0) {
> +        // XD enabled
> +        if ((AsmReadMsr64 (0xC0000080) & BIT11) != 0) {
> +          // XD activated
> +          PagingContext->ContextData.Ia32.Attributes |= PAGE_TABLE_LIB_PAGING_CONTEXT_IA32_X64_ATTRIBUTES_XD_ACTIVATED;
> +        }
> +      }
> +    }

>From OVMF output:

!!!! X64 Exception Type - 0D(#GP - General Protection)  CPU Apic ID - 00000000 !!!!
RIP  - 000000002F323ABE, CS  - 0000000000000018, RFLAGS - 0000000000010002
ExceptionData - 0000000000000000
RAX  - 0000000080000001, RCX - 00000000000001A0, RDX - 000000002FD3FBFF
RBX  - 000000002F422CB8, RSP - 000000002F422C68, RBP - 000000002EE0AD98
RSI  - 000000002F3AF018, RDI - 000000002F3229E4
R8   - 0000000000000000, R9  - 0000000000000000, R10 - 0000000000000000
R11  - 000000002F422BAD, R12 - 0000000000000000, R13 - 0000000000000000
R14  - 0000000000000000, R15 - 000000002F44A980
DS   - 0000000000000008, ES  - 0000000000000008, FS  - 0000000000000008
GS   - 0000000000000008, SS  - 0000000000000008
CR0  - 00000000C0010033, CR2 - 0000000000000000, CR3 - 000000002F3C1000
CR4  - 0000000000000668, CR8 - 0000000000000000
DR0  - 0000000000000000, DR1 - 0000000000000000, DR2 - 0000000000000000
DR3  - 0000000000000000, DR6 - 00000000FFFF0FF0, DR7 - 0000000000000400
GDTR - 00000000FFFFFF80 000000000000001F, LDTR - 0000000000000000
IDTR - 000000002B68DD90 000000000000021F,   TR - 0000000000000000
FXSAVE_STATE - 000000002F4228C0
!!!! Find PE image /home/osstest/build.106538.build-amd64/xen/tools/firmware/ovmf-dir-remote/Build/OvmfX64/DEBUG_GCC49/X64/UefiCpuPkg/CpuDxe/CpuDxe/DEBUG/CpuDxe.dll (ImageBase=000000002F321000, EntryPoint=000000002F321271) !!!!


Thanks,

-- 
Anthony PERARD