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xen
6672c847-x86-CPUID-XSAVE-dynamic-leaves.patch
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File 6672c847-x86-CPUID-XSAVE-dynamic-leaves.patch of Package xen
# Commit 71cacfb035f4a78ee10970dc38a3baa04d387451 # Date 2024-06-19 13:00:06 +0100 # Author Andrew Cooper <andrew.cooper3@citrix.com> # Committer Andrew Cooper <andrew.cooper3@citrix.com> x86/cpuid: Fix handling of XSAVE dynamic leaves [ This is a minimal backport of commit 71cacfb035f4 ("x86/cpuid: Fix handling of XSAVE dynamic leaves") to fix the bugs without depending on the large rework of XSTATE handling in Xen 4.19 ] First, if XSAVE is available in hardware but not visible to the guest, the dynamic leaves shouldn't be filled in. Second, the comment concerning XSS state is wrong. VT-x doesn't manage host/guest state automatically, but there is provision for "host only" bits to be set, so the implications are still accurate. In Xen 4.18, no XSS states are supported, so it's safe to keep deferring to real hardware. Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> --- a/xen/arch/x86/cpuid.c +++ b/xen/arch/x86/cpuid.c @@ -330,24 +330,20 @@ void guest_cpuid(const struct vcpu *v, u case XSTATE_CPUID: switch ( subleaf ) { - case 1: - if ( p->xstate.xsavec || p->xstate.xsaves ) - { - /* - * TODO: Figure out what to do for XSS state. VT-x manages - * host vs guest MSR_XSS automatically, so as soon as we start - * supporting any XSS states, the wrong XSS will be in - * context. - */ - BUILD_BUG_ON(XSTATE_XSAVES_ONLY != 0); - - /* - * Read CPUID[0xD,0/1].EBX from hardware. They vary with - * enabled XSTATE, and appropraite XCR0|XSS are in context. - */ + /* + * Read CPUID[0xd,0/1].EBX from hardware. They vary with enabled + * XSTATE, and the appropriate XCR0 is in context. + */ case 0: - res->b = cpuid_count_ebx(leaf, subleaf); - } + if ( p->basic.xsave ) + res->b = cpuid_count_ebx(0xd, 0); + break; + + case 1: + /* This only works because Xen doesn't support XSS states yet. */ + BUILD_BUG_ON(XSTATE_XSAVES_ONLY != 0); + if ( p->xstate.xsavec ) + res->b = cpuid_count_ebx(0xd, 1); break; } break;
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