[PATCH v2 1/8] x86/fpu/xstate: Define new macros for supervisor and user xstates

From: Yu-cheng Yu
Date: Tue Jan 21 2020 - 15:20:07 EST

From: Fenghua Yu <fenghua.yu@xxxxxxxxx>

XCNTXT_MASK is 'all supported xfeatures' before introducing supervisor
xstates. Rename it to SUPPORTED_XFEATURES_MASK_USER to make clear that
these are user xstates.

XFEATURE_MASK_SUPERVISOR is replaced with the following:
- SUPPORTED_XFEATURES_MASK_SUPERVISOR: Currently nothing. ENQCMD and
Control-flow Enforcement Technology (CET) will be introduced in separate
series.
- UNSUPPORTED_XFEATURES_MASK_SUPERVISOR: Currently only Processor Trace.
- ALL_XFEATURES_MASK_SUPERVISOR: the combination of above.

Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Co-developed-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
---
arch/x86/include/asm/fpu/xstate.h | 36 ++++++++++++++++++++-----------
arch/x86/kernel/fpu/init.c | 3 ++-
arch/x86/kernel/fpu/xstate.c | 26 +++++++++++-----------
3 files changed, 38 insertions(+), 27 deletions(-)

diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index c6136d79f8c0..014c386deaa3 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -21,19 +21,29 @@
#define XSAVE_YMM_SIZE 256
#define XSAVE_YMM_OFFSET (XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET)

-/* Supervisor features */
-#define XFEATURE_MASK_SUPERVISOR (XFEATURE_MASK_PT)
-
-/* All currently supported features */
-#define XCNTXT_MASK (XFEATURE_MASK_FP | \
- XFEATURE_MASK_SSE | \
- XFEATURE_MASK_YMM | \
- XFEATURE_MASK_OPMASK | \
- XFEATURE_MASK_ZMM_Hi256 | \
- XFEATURE_MASK_Hi16_ZMM | \
- XFEATURE_MASK_PKRU | \
- XFEATURE_MASK_BNDREGS | \
- XFEATURE_MASK_BNDCSR)
+/* All currently supported user features */
+#define SUPPORTED_XFEATURES_MASK_USER (XFEATURE_MASK_FP | \
+ XFEATURE_MASK_SSE | \
+ XFEATURE_MASK_YMM | \
+ XFEATURE_MASK_OPMASK | \
+ XFEATURE_MASK_ZMM_Hi256 | \
+ XFEATURE_MASK_Hi16_ZMM | \
+ XFEATURE_MASK_PKRU | \
+ XFEATURE_MASK_BNDREGS | \
+ XFEATURE_MASK_BNDCSR)
+
+/* All currently supported supervisor features */
+#define SUPPORTED_XFEATURES_MASK_SUPERVISOR (0)
+
+/*
+ * Unsupported supervisor features. When a supervisor feature in this mask is
+ * supported in the future, move it to the supported supervisor feature mask.
+ */
+#define UNSUPPORTED_XFEATURES_MASK_SUPERVISOR (XFEATURE_MASK_PT)
+
+/* All supervisor states including supported and unsupported states. */
+#define ALL_XFEATURES_MASK_SUPERVISOR (SUPPORTED_XFEATURES_MASK_SUPERVISOR | \
+ UNSUPPORTED_XFEATURES_MASK_SUPERVISOR)

#ifdef CONFIG_X86_64
#define REX_PREFIX "0x48, "
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 6ce7e0a23268..ba3705d25162 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -224,7 +224,8 @@ static void __init fpu__init_system_xstate_size_legacy(void)
*/
u64 __init fpu__get_supported_xfeatures_mask(void)
{
- return XCNTXT_MASK;
+ return SUPPORTED_XFEATURES_MASK_USER |
+ SUPPORTED_XFEATURES_MASK_SUPERVISOR;
}

/* Legacy code to initialize eager fpu mode. */
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 4fa494073289..7d8e9414efa4 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -213,14 +213,13 @@ void fpu__init_cpu_xstate(void)
if (!boot_cpu_has(X86_FEATURE_XSAVE) || !xfeatures_mask)
return;
/*
- * Make it clear that XSAVES supervisor states are not yet
- * implemented should anyone expect it to work by changing
- * bits in XFEATURE_MASK_* macros and XCR0.
+ * Unsupported supervisor xstates should not be found in
+ * the xfeatures mask.
*/
- WARN_ONCE((xfeatures_mask & XFEATURE_MASK_SUPERVISOR),
- "x86/fpu: XSAVES supervisor states are not yet implemented.\n");
+ WARN_ONCE((xfeatures_mask & UNSUPPORTED_XFEATURES_MASK_SUPERVISOR),
+ "x86/fpu: Found unsupported supervisor xstates.\n");

- xfeatures_mask &= ~XFEATURE_MASK_SUPERVISOR;
+ xfeatures_mask &= ~UNSUPPORTED_XFEATURES_MASK_SUPERVISOR;

cr4_set_bits(X86_CR4_OSXSAVE);
xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
@@ -443,7 +442,7 @@ static int xfeature_uncompacted_offset(int xfeature_nr)
* format. Checking a supervisor state's uncompacted offset is
* an error.
*/
- if (XFEATURE_MASK_SUPERVISOR & BIT_ULL(xfeature_nr)) {
+ if (ALL_XFEATURES_MASK_SUPERVISOR & BIT_ULL(xfeature_nr)) {
WARN_ONCE(1, "No fixed offset for xstate %d\n", xfeature_nr);
return -1;
}
@@ -480,7 +479,7 @@ int using_compacted_format(void)
int validate_xstate_header(const struct xstate_header *hdr)
{
/* No unknown or supervisor features may be set */
- if (hdr->xfeatures & (~xfeatures_mask | XFEATURE_MASK_SUPERVISOR))
+ if (hdr->xfeatures & ~(xfeatures_mask & SUPPORTED_XFEATURES_MASK_USER))
return -EINVAL;

/* Userspace must use the uncompacted format */
@@ -773,7 +772,8 @@ void __init fpu__init_system_xstate(void)
* Update info used for ptrace frames; use standard-format size and no
* supervisor xstates:
*/
- update_regset_xstate_info(fpu_user_xstate_size, xfeatures_mask & ~XFEATURE_MASK_SUPERVISOR);
+ update_regset_xstate_info(fpu_user_xstate_size,
+ xfeatures_mask & SUPPORTED_XFEATURES_MASK_USER);

fpu__init_prepare_fx_sw_frame();
setup_init_fpu_buf();
@@ -996,7 +996,7 @@ int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int of
*/
memset(&header, 0, sizeof(header));
header.xfeatures = xsave->header.xfeatures;
- header.xfeatures &= ~XFEATURE_MASK_SUPERVISOR;
+ header.xfeatures &= SUPPORTED_XFEATURES_MASK_USER;

/*
* Copy xregs_state->header:
@@ -1080,7 +1080,7 @@ int copy_xstate_to_user(void __user *ubuf, struct xregs_state *xsave, unsigned i
*/
memset(&header, 0, sizeof(header));
header.xfeatures = xsave->header.xfeatures;
- header.xfeatures &= ~XFEATURE_MASK_SUPERVISOR;
+ header.xfeatures &= SUPPORTED_XFEATURES_MASK_USER;

/*
* Copy xregs_state->header:
@@ -1173,7 +1173,7 @@ int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf)
* The state that came in from userspace was user-state only.
* Mask all the user states out of 'xfeatures':
*/
- xsave->header.xfeatures &= XFEATURE_MASK_SUPERVISOR;
+ xsave->header.xfeatures &= ALL_XFEATURES_MASK_SUPERVISOR;

/*
* Add back in the features that came in from userspace:
@@ -1229,7 +1229,7 @@ int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
* The state that came in from userspace was user-state only.
* Mask all the user states out of 'xfeatures':
*/
- xsave->header.xfeatures &= XFEATURE_MASK_SUPERVISOR;
+ xsave->header.xfeatures &= ALL_XFEATURES_MASK_SUPERVISOR;

/*
* Add back in the features that came in from userspace:
--
2.21.0