The following commit has been merged into the x86/fpu branch of tip:
Commit-ID: 71581eefd7a0a81b1af7d7c93641925a01d70a9a
Gitweb: https://git.kernel.org/tip/71581eefd7a0a81b1af7d7c93641925a01d70a9a
Author: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
AuthorDate: Tue, 12 May 2020 07:54:38 -07:00
Committer: Borislav Petkov <bp@xxxxxxx>
CommitterDate: Wed, 13 May 2020 12:16:47 +02:00
x86/fpu/xstate: Introduce XSAVES supervisor states
Enable XSAVES supervisor states by setting MSR_IA32_XSS bits according
to CPUID enumeration results. Also revise comments at various places.
Co-developed-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
Link: https://lkml.kernel.org/r/20200512145444.15483-5-yu-cheng.yu@xxxxxxxxx
---
arch/x86/kernel/fpu/xstate.c | 28 +++++++++++++++++++---------
1 file changed, 19 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index fa71af6..a68213e 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -228,13 +228,14 @@ void fpu__init_cpu_xstate(void)
* states can be set here.
*/
xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask_user());
+
+ /*
+ * MSR_IA32_XSS sets supervisor states managed by XSAVES.
+ */
+ if (boot_cpu_has(X86_FEATURE_XSAVES))
+ wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor());
}
-/*
- * Note that in the future we will likely need a pair of
- * functions here: one for user xstates and the other for
- * system xstates. For now, they are the same.
- */
static bool xfeature_enabled(enum xfeature xfeature)
{
return xfeatures_mask_all & BIT_ULL(xfeature);
@@ -625,9 +626,6 @@ static void do_extra_xstate_size_checks(void)
* the size of the *user* states. If we use it to size a buffer
* that we use 'XSAVES' on, we could potentially overflow the
* buffer because 'XSAVES' saves system states too.
- *
- * Note that we do not currently set any bits on IA32_XSS so
- * 'XCR0 | IA32_XSS == XCR0' for now.
*/
static unsigned int __init get_xsaves_size(void)
{
@@ -750,7 +748,12 @@ void __init fpu__init_system_xstate(void)
cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
xfeatures_mask_all = eax + ((u64)edx << 32);
- /* Place supervisor features in xfeatures_mask_all here */
+ /*
+ * Find supervisor xstates supported by the processor.
+ */
+ cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
+ xfeatures_mask_all |= ecx + ((u64)edx << 32);
+
if ((xfeatures_mask_user() & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
/*
* This indicates that something really unexpected happened
@@ -810,6 +813,13 @@ void fpu__resume_cpu(void)
*/
if (boot_cpu_has(X86_FEATURE_XSAVE))
xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask_user());
+
+ /*
+ * Restore IA32_XSS. The same CPUID bit enumerates support
+ * of XSAVES and MSR_IA32_XSS.
+ */
+ if (boot_cpu_has(X86_FEATURE_XSAVES))
+ wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor());
}
/*
|