[PATCH v9 03/26] x86/fpu/xstate: Modify address finders to handle both static and dynamic buffers

Chang S. Bae
2021-07-30T15:06:30Z

Have all the functions finding XSTATE address take a struct fpu * pointer
in preparation for dynamic state buffer support.

init_fpstate is a special case, which is indicated by a null pointer
parameter to get_xsave_addr() and __raw_xsave_addr().

No functional change.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Reviewed-by: Len Brown <len.brown@intel.com>
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: kvm@vger.kernel.org
---
Changes from v5:
* Adjusted some call sites for the new base.

Changes from v3:
* Updated the changelog. (Borislav Petkov)
* Updated the function comment to use kernel-doc style. (Borislav Petkov)

Changes from v2:
* Updated the changelog with task->fpu removed. (Borislav Petkov)

Changes from v1:
* Rebased on the upstream kernel (5.10)
---
arch/x86/include/asm/fpu/xstate.h | 2 +-
arch/x86/kernel/fpu/xstate.c | 42 ++++++++++++++++++++++++-------
arch/x86/kvm/x86.c | 10 +++-----
3 files changed, 38 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index ede166e9d3f2..2451bccc6cac 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -134,7 +134,7 @@ extern u64 xstate_fx_sw_bytes[USER_XSTATE_FX_SW_WORDS];
extern void __init update_regset_xstate_info(unsigned int size,
u64 xstate_mask);

-void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr);
+void *get_xsave_addr(struct fpu *fpu, int xfeature_nr);
int xfeature_size(int xfeature_nr);
int copy_uabi_from_kernel_to_xstate(struct fpu *fpu, const void *kbuf);
int copy_sigframe_from_user_to_xstate(struct fpu *fpu, const void __user *ubuf);
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 59f08953201c..d9c029ab9497 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -841,19 +841,34 @@ void fpu__resume_cpu(void)
}
}

-/*
+/**
+ * __raw_xsave_addr - Find the address where the feature state is saved.
+ *
* Given an xstate feature nr, calculate where in the xsave
* buffer the state is. Callers should ensure that the buffer
* is valid.
+ *
+ * If @fpu is NULL, use init_fpstate.
+ *
+ * @fpu: A struct fpu * pointer
+ *
+ * Return: An address of the feature state in the buffer
*/
-static void *__raw_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
+static void *__raw_xsave_addr(struct fpu *fpu, int xfeature_nr)
{
+ void *xsave;
+
if (!xfeature_enabled(xfeature_nr)) {
WARN_ON_FPU(1);
return NULL;
}

- return (void *)xsave + xstate_comp_offsets[xfeature_nr];
+ if (fpu)
+ xsave = &fpu->state.xsave;
+ else
+ xsave = &init_fpstate.xsave;
+
+ return xsave + xstate_comp_offsets[xfeature_nr];
}
/*
* Given the xsave area and a state inside, this function returns the
@@ -866,15 +881,18 @@ static void *__raw_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
* this will return NULL.
*
* Inputs:
- * xstate: the thread's storage area for all FPU data
+ * fpu: the thread's FPU data to reference xstate buffer(s).
+ * (A null pointer parameter indicates init_fpstate.)
* xfeature_nr: state which is defined in xsave.h (e.g. XFEATURE_FP,
* XFEATURE_SSE, etc...)
* Output:
* address of the state in the xsave area, or NULL if the
* field is not present in the xsave buffer.
*/
-void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
+void *get_xsave_addr(struct fpu *fpu, int xfeature_nr)
{
+ struct xregs_state *xsave;
+
/*
* Do we even *have* xsave state?
*/
@@ -887,6 +905,12 @@ void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
*/
WARN_ONCE(!(xfeatures_mask_all & BIT_ULL(xfeature_nr)),
"get of unsupported state");
+
+ if (fpu)
+ xsave = &fpu->state.xsave;
+ else
+ xsave = &init_fpstate.xsave;
+
/*
* This assumes the last 'xsave*' instruction to
* have requested that 'xfeature_nr' be saved.
@@ -901,7 +925,7 @@ void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
if (!(xsave->header.xfeatures & BIT_ULL(xfeature_nr)))
return NULL;

- return __raw_xsave_addr(xsave, xfeature_nr);
+ return __raw_xsave_addr(fpu, xfeature_nr);
}
EXPORT_SYMBOL_GPL(get_xsave_addr);

@@ -1061,8 +1085,8 @@ void copy_xstate_to_uabi_buf(struct membuf to, struct task_struct *tsk,
membuf_write(&to, &pkru, sizeof(pkru));
} else {
copy_feature(header.xfeatures & BIT_ULL(i), &to,
- __raw_xsave_addr(xsave, i),
- __raw_xsave_addr(xinit, i),
+ __raw_xsave_addr(&tsk->thread.fpu, i),
+ __raw_xsave_addr(NULL, i),
xstate_sizes[i]);
}
/*
@@ -1129,7 +1153,7 @@ static int copy_uabi_to_xstate(struct fpu *fpu, const void *kbuf,
u64 mask = ((u64)1 << i);

if (hdr.xfeatures & mask) {
- void *dst = __raw_xsave_addr(xsave, i);
+ void *dst = __raw_xsave_addr(fpu, i);

offset = xstate_offsets[i];
size = xstate_sizes[i];
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 76a4e5e274d8..c72e3ad0f9b8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4717,7 +4717,7 @@ static void fill_xsave(u8 *dest, struct kvm_vcpu *vcpu)
memcpy(dest + offset, &vcpu->arch.pkru,
sizeof(vcpu->arch.pkru));
} else {
- src = get_xsave_addr(xsave, xfeature_nr);
+ src = get_xsave_addr(vcpu->arch.guest_fpu, xfeature_nr);
if (src)
memcpy(dest + offset, src, size);
}
@@ -4760,7 +4760,7 @@ static void load_xsave(struct kvm_vcpu *vcpu, u8 *src)
memcpy(&vcpu->arch.pkru, src + offset,
sizeof(vcpu->arch.pkru));
} else {
- void *dest = get_xsave_addr(xsave, xfeature_nr);
+ void *dest = get_xsave_addr(vcpu->arch.guest_fpu, xfeature_nr);

if (dest)
memcpy(dest, src + offset, size);
@@ -10831,12 +10831,10 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
*/
if (init_event)
kvm_put_guest_fpu(vcpu);
- mpx_state_buffer = get_xsave_addr(&vcpu->arch.guest_fpu->state.xsave,
- XFEATURE_BNDREGS);
+ mpx_state_buffer = get_xsave_addr(vcpu->arch.guest_fpu, XFEATURE_BNDREGS);
if (mpx_state_buffer)
memset(mpx_state_buffer, 0, sizeof(struct mpx_bndreg_state));
- mpx_state_buffer = get_xsave_addr(&vcpu->arch.guest_fpu->state.xsave,
- XFEATURE_BNDCSR);
+ mpx_state_buffer = get_xsave_addr(vcpu->arch.guest_fpu, XFEATURE_BNDCSR);
if (mpx_state_buffer)
memset(mpx_state_buffer, 0, sizeof(struct mpx_bndcsr));
if (init_event)
--
2.17.1