Use fpu_guest_cfg to calculate guest fpstate settings, open code for
__fpstate_reset() to avoid using kernel FPU config.
Below configuration steps are currently enforced to get guest fpstate:
1) Kernel sets up guest FPU settings in fpu__init_system_xstate().
2) User space sets vCPU thread group xstate permits via arch_prctl().
3) User space creates guest fpstate via __fpu_alloc_init_guest_fpstate()
for vcpu thread.
4) User space enables guest dynamic xfeatures and re-allocate guest
fpstate.
By adding kernel dynamic xfeatures in above #1 and #2, guest xstate area
size is expanded to hold (fpu_kernel_cfg.default_features | kernel dynamic
xfeatures | user dynamic xfeatures), then host xsaves/xrstors can operate
for all guest xfeatures.
The user_* fields remain unchanged for compatibility with KVM uAPIs.
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
arch/x86/kernel/fpu/core.c | 48 ++++++++++++++++++++++++++++--------
arch/x86/kernel/fpu/xstate.c | 2 +-
arch/x86/kernel/fpu/xstate.h | 1 +
3 files changed, 40 insertions(+), 11 deletions(-)
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 516af626bf6a..985eaf8b55e0 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -194,8 +194,6 @@ void fpu_reset_from_exception_fixup(void)
}
#if IS_ENABLED(CONFIG_KVM)
-static void __fpstate_reset(struct fpstate *fpstate, u64 xfd);
-
static void fpu_init_guest_permissions(struct fpu_guest *gfpu)
{
struct fpu_state_perm *fpuperm;
@@ -216,25 +214,55 @@ static void fpu_init_guest_permissions(struct fpu_guest *gfpu)
gfpu->perm = perm & ~FPU_GUEST_PERM_LOCKED;
}
-bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
+static struct fpstate *__fpu_alloc_init_guest_fpstate(struct fpu_guest *gfpu)
{
+ bool compacted = cpu_feature_enabled(X86_FEATURE_XCOMPACTED);
+ unsigned int gfpstate_size, size;
struct fpstate *fpstate;
- unsigned int size;
- size = fpu_user_cfg.default_size + ALIGN(offsetof(struct fpstate, regs), 64);
+ /*
+ * fpu_guest_cfg.default_features includes all enabled xfeatures
+ * except the user dynamic xfeatures. If the user dynamic xfeatures
+ * are enabled, the guest fpstate will be re-allocated to hold all
+ * guest enabled xfeatures, so omit user dynamic xfeatures here.
+ */
+ gfpstate_size = xstate_calculate_size(fpu_guest_cfg.default_features,
+ compacted);
+
+ size = gfpstate_size + ALIGN(offsetof(struct fpstate, regs), 64);
+
fpstate = vzalloc(size);
if (!fpstate)
- return false;
+ return NULL;
+ /*
+ * Initialize sizes and feature masks, use fpu_user_cfg.*
+ * for user_* settings for compatibility of exiting uAPIs.
+ */
+ fpstate->size = gfpstate_size;
+ fpstate->xfeatures = fpu_guest_cfg.default_features;
+ fpstate->user_size = fpu_user_cfg.default_size;
+ fpstate->user_xfeatures = fpu_user_cfg.default_features;
+ fpstate->xfd = 0;
- /* Leave xfd to 0 (the reset value defined by spec) */
- __fpstate_reset(fpstate, 0);
fpstate_init_user(fpstate);
fpstate->is_valloc = true;
fpstate->is_guest = true;
gfpu->fpstate = fpstate;
- gfpu->xfeatures = fpu_user_cfg.default_features;
- gfpu->perm = fpu_user_cfg.default_features;
+ gfpu->xfeatures = fpu_guest_cfg.default_features;
+ gfpu->perm = fpu_guest_cfg.default_features;
+
+ return fpstate;
+}
+
+bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
+{
+ struct fpstate *fpstate;
+
+ fpstate = __fpu_alloc_init_guest_fpstate(gfpu);
+
+ if (!fpstate)
+ return false;
/*
* KVM sets the FP+SSE bits in the XSAVE header when copying FPU state
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index aa8f8595cd41..253944cb2298 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -559,7 +559,7 @@ static bool __init check_xstate_against_struct(int nr)
return true;
}
-static unsigned int xstate_calculate_size(u64 xfeatures, bool compacted)
+unsigned int xstate_calculate_size(u64 xfeatures, bool compacted)
{
unsigned int topmost = fls64(xfeatures) - 1;
unsigned int offset = xstate_offsets[topmost];
diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h
index 3518fb26d06b..c032acb56306 100644
--- a/arch/x86/kernel/fpu/xstate.h
+++ b/arch/x86/kernel/fpu/xstate.h
@@ -55,6 +55,7 @@ extern void fpu__init_cpu_xstate(void);
extern void fpu__init_system_xstate(unsigned int legacy_size);
extern void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr);
+extern unsigned int xstate_calculate_size(u64 xfeatures, bool compacted);
static inline u64 xfeatures_mask_supervisor(void)
{
--
2.27.0
