On 2018-04-16 19:46, Francois-Frederic Ozog wrote:
> From: Francois-Frederic Ozog <francois.o...@linaro.org>
>
> inmates cannot use X86_FEATURE_VMX from regular cpuid
> as vcpu maks the bit explicitely on non-root cells.
>
> use cpuid leaf 0 to detect AuthenticAMD and change to VMMCALL
>
> use string compare for clearer code
>
> Signed-off-by: Francois-Frederic Ozog <francois.o...@linaro.org>
> ---
> inmates/lib/x86/hypercall.c | 21 ++++++++++++++-------
> 1 file changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/inmates/lib/x86/hypercall.c b/inmates/lib/x86/hypercall.c
> index ac99f0c3..07529d4d 100644
> --- a/inmates/lib/x86/hypercall.c
> +++ b/inmates/lib/x86/hypercall.c
> @@ -40,19 +40,26 @@
>
> #define X86_FEATURE_VMX (1 << 5)
>
> -bool jailhouse_use_vmcall;
> +bool jailhouse_use_vmcall = true;
> +
> +static const char* AUTHENTIC_AMD = "AuthenticAMD";
> +#define U32_SUBSTR(s, n) (((const u32*)s)[n])
>
> void hypercall_init(void)
> {
> - u32 eax = 1, ecx = 0;
> + u32 ebx, ecx, edx;
>
> asm volatile(
> + "xor %%eax, %%eax \n\t"
> "cpuid"
> - : "=c" (ecx)
> - : "a" (eax), "c" (ecx)
> - : "rbx", "rdx", "memory"
> + : "=b" (ebx), "=c" (ecx), "=d" (edx)
> + :
> + : "memory"
> );
>
> - if (ecx & X86_FEATURE_VMX)
> - jailhouse_use_vmcall = true;
> + if (ebx == U32_SUBSTR(AUTHENTIC_AMD, 0)
> + && ecx == U32_SUBSTR(AUTHENTIC_AMD, 2)
> + && edx == U32_SUBSTR(AUTHENTIC_AMD, 1)
> + )
> + jailhouse_use_vmcall = false;
> }
>
I would go with this diff now unless you have concerns:
diff --git a/inmates/lib/x86/hypercall.c b/inmates/lib/x86/hypercall.c
index ac99f0c3e..fc5cd5ac8 100644
--- a/inmates/lib/x86/hypercall.c
+++ b/inmates/lib/x86/hypercall.c
@@ -38,21 +38,24 @@
#include <inmate.h>
-#define X86_FEATURE_VMX (1 << 5)
+#define X86_FEATURE_VMX (1 << 5)
-bool jailhouse_use_vmcall;
+bool jailhouse_use_vmcall = true;
+
+#define AUTHENTIC_AMD(n) (((const u32 *)"AuthenticAMD")[n])
void hypercall_init(void)
{
- u32 eax = 1, ecx = 0;
+ u32 eax, ebx, ecx, edx;
- asm volatile(
- "cpuid"
- : "=c" (ecx)
- : "a" (eax), "c" (ecx)
- : "rbx", "rdx", "memory"
+ asm volatile("cpuid"
+ : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx)
+ : "a" (0)
+ : "memory"
);
- if (ecx & X86_FEATURE_VMX)
- jailhouse_use_vmcall = true;
+ if (ebx == AUTHENTIC_AMD(0) &&
+ edx == AUTHENTIC_AMD(1) &&
+ ecx == AUTHENTIC_AMD(2))
+ jailhouse_use_vmcall = false;
}
We need to account for Intel cpuid clobbering eax. Moreover, I played a
bit with the style. Newer gcc even avoids a static string.
Still need to validate this on an AMD system, though.
Thanks,
Jan
--
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux
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