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