From: WANG Xuerui <[email protected]>
Hi,
(Sorry for the noise; in the previous revision the patch 1 contained a
syntax error. I've also added a Fixes: tag for the KVM LASX support
commit while at it.)
While trying to add loongarch to the Rust kvm-bindings crate, I
accidentally discovered faulty logic in the handling of CPUCFG IDs
("leaves" for those more familiar with x86), that could result in
incorrectly accepting every possible int for the ID; fortunately it is
6.8 material that hasn't seen a release yet, so a fix is possible.
The first patch contains the fix, while the rest are general
drive-by refactoring and comment cleanups.
Although it is currently the Chinese holiday season, Huacai told me
over IM that he's able to test the series and handle the upstreaming, so
going through the loongarch tree seems to be the way forward for the
series.
v3 changes:
- Fixed the validation by accepting every CPUCFG IDs from 0 to 20
inclusive, instead of only 2; this was a misunderstanding of mine
regarding the userland. (currently the only known user, the QEMU
target/loongarch KVM code, expects to be able to set all these 21
CPUCFG leaves, even though 7~15 are undefined according to the
LoongArch reference manual.) This also had the effect of squashing the
first 2 patches.
- Made the _kvm_get_cpucfg_mask return a mask in all valid cases,
allowing the mask check to be lifted out of the CPUCFG2 case.
- Swapped the "LoongArch:" and "KVM:" tags because right now the patches
are likely to reach mainline through the loongarch tree, and having
the "LoongArch:" prefix first is the convention here.
v2 changes:
- Squashed the v1 patches 4 and 5 according to Huacai's review
- Reworded comments according to Huacai's suggestion
- Use WARN_ON_ONCE (instead of BUG) to replace unreachable() for not
crashing the kernel (per checkpatch.pl suggestion)
WANG Xuerui (3):
LoongArch: KVM: Fix input validation of _kvm_get_cpucfg and
kvm_check_cpucfg
LoongArch: KVM: Rename _kvm_get_cpucfg to _kvm_get_cpucfg_mask
LoongArch: KVM: Streamline kvm_check_cpucfg and improve comments
arch/loongarch/kvm/vcpu.c | 81 ++++++++++++++++++---------------------
1 file changed, 38 insertions(+), 43 deletions(-)
--
2.43.0
From: WANG Xuerui <[email protected]>
The function is not actually a getter of guest CPUCFG, but rather
validation of the input CPUCFG ID plus information about the supported
bit flags of that CPUCFG leaf. So rename it to avoid confusion.
Signed-off-by: WANG Xuerui <[email protected]>
---
arch/loongarch/kvm/vcpu.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
index 124cd7a75061..e5acd4c08071 100644
--- a/arch/loongarch/kvm/vcpu.c
+++ b/arch/loongarch/kvm/vcpu.c
@@ -298,7 +298,7 @@ static int _kvm_setcsr(struct kvm_vcpu *vcpu, unsigned int id, u64 val)
return ret;
}
-static int _kvm_get_cpucfg(int id, u64 *v)
+static int _kvm_get_cpucfg_mask(int id, u64 *v)
{
switch (id) {
case 2:
@@ -335,7 +335,7 @@ static int kvm_check_cpucfg(int id, u64 val)
u64 mask = 0;
int ret;
- ret = _kvm_get_cpucfg(id, &mask);
+ ret = _kvm_get_cpucfg_mask(id, &mask);
if (ret)
return ret;
@@ -563,7 +563,7 @@ static int kvm_loongarch_get_cpucfg_attr(struct kvm_vcpu *vcpu,
uint64_t val;
uint64_t __user *uaddr = (uint64_t __user *)attr->addr;
- ret = _kvm_get_cpucfg(attr->attr, &val);
+ ret = _kvm_get_cpucfg_mask(attr->attr, &val);
if (ret)
return ret;
--
2.43.0
From: WANG Xuerui <[email protected]>
The range check for the CPUCFG ID is wrong (should have been a ||
instead of &&); it is conceptually simpler to just express the check
as another case of the switch statement on the ID. As it turns out to be
the case, the userland (currently only the QEMU/KVM target code) expects
to set CPUCFG IDs 0 to 20 inclusive, but only CPUCFG2 values are being
validated.
Furthermore, the juggling of the temp return value is unnecessary,
because it is semantically equivalent and more readable to just
return at every switch case's end. This is done too to avoid potential
bugs in the future related to the unwanted complexity.
Also, the return value of _kvm_get_cpucfg is meant to be checked, but
this was not done, so bad CPUCFG IDs wrongly fall back to the default
case and 0 is incorrectly returned; check the return value to fix the
UAPI behavior.
While at it, also remove the redundant range check in kvm_check_cpucfg,
because out-of-range CPUCFG IDs are already rejected by the -EINVAL
as returned by _kvm_get_cpucfg.
Fixes: db1ecca22edf ("LoongArch: KVM: Add LSX (128bit SIMD) support")
Fixes: 118e10cd893d ("LoongArch: KVM: Add LASX (256bit SIMD) support")
Signed-off-by: WANG Xuerui <[email protected]>
---
arch/loongarch/kvm/vcpu.c | 35 ++++++++++++++++-------------------
1 file changed, 16 insertions(+), 19 deletions(-)
diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
index 27701991886d..124cd7a75061 100644
--- a/arch/loongarch/kvm/vcpu.c
+++ b/arch/loongarch/kvm/vcpu.c
@@ -300,11 +300,6 @@ static int _kvm_setcsr(struct kvm_vcpu *vcpu, unsigned int id, u64 val)
static int _kvm_get_cpucfg(int id, u64 *v)
{
- int ret = 0;
-
- if (id < 0 && id >= KVM_MAX_CPUCFG_REGS)
- return -EINVAL;
-
switch (id) {
case 2:
/* Return CPUCFG2 features which have been supported by KVM */
@@ -324,32 +319,34 @@ static int _kvm_get_cpucfg(int id, u64 *v)
if (cpu_has_lasx)
*v |= CPUCFG2_LASX;
- break;
+ return 0;
+ case 0 ... 1:
+ case 3 ... KVM_MAX_CPUCFG_REGS - 1:
+ /* no restrictions on other CPUCFG IDs' values */
+ *v = U64_MAX;
+ return 0;
default:
- ret = -EINVAL;
- break;
+ return -EINVAL;
}
- return ret;
}
static int kvm_check_cpucfg(int id, u64 val)
{
- u64 mask;
- int ret = 0;
-
- if (id < 0 && id >= KVM_MAX_CPUCFG_REGS)
- return -EINVAL;
+ u64 mask = 0;
+ int ret;
- if (_kvm_get_cpucfg(id, &mask))
+ ret = _kvm_get_cpucfg(id, &mask);
+ if (ret)
return ret;
+ if (val & ~mask)
+ /* Unsupported features should not be set */
+ return -EINVAL;
+
switch (id) {
case 2:
/* CPUCFG2 features checking */
- if (val & ~mask)
- /* The unsupported features should not be set */
- ret = -EINVAL;
- else if (!(val & CPUCFG2_LLFTP))
+ if (!(val & CPUCFG2_LLFTP))
/* The LLFTP must be set, as guest must has a constant timer */
ret = -EINVAL;
else if ((val & CPUCFG2_FP) && (!(val & CPUCFG2_FPSP) || !(val & CPUCFG2_FPDP)))
--
2.43.0
From: WANG Xuerui <[email protected]>
All the checks currently done in kvm_check_cpucfg can be realized with
early returns, so just do that to avoid extra cognitive burden related
to the return value handling.
While at it, clean up comments of _kvm_get_cpucfg_mask and
kvm_check_cpucfg, by removing comments that are merely restatement of
the code nearby, and paraphrasing the rest so they read more natural
for English speakers (that likely are not familiar with the actual
Chinese-influenced grammar).
No functional changes intended.
Signed-off-by: WANG Xuerui <[email protected]>
---
arch/loongarch/kvm/vcpu.c | 42 +++++++++++++++++++--------------------
1 file changed, 20 insertions(+), 22 deletions(-)
diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
index e5acd4c08071..a241db6d77a6 100644
--- a/arch/loongarch/kvm/vcpu.c
+++ b/arch/loongarch/kvm/vcpu.c
@@ -302,20 +302,16 @@ static int _kvm_get_cpucfg_mask(int id, u64 *v)
{
switch (id) {
case 2:
- /* Return CPUCFG2 features which have been supported by KVM */
+ /* CPUCFG2 features unconditionally supported by KVM */
*v = CPUCFG2_FP | CPUCFG2_FPSP | CPUCFG2_FPDP |
CPUCFG2_FPVERS | CPUCFG2_LLFTP | CPUCFG2_LLFTPREV |
CPUCFG2_LAM;
/*
- * If LSX is supported by CPU, it is also supported by KVM,
- * as we implement it.
+ * For the ISA extensions listed below, if one is supported
+ * by the host, then it is also supported by KVM.
*/
if (cpu_has_lsx)
*v |= CPUCFG2_LSX;
- /*
- * if LASX is supported by CPU, it is also supported by KVM,
- * as we implement it.
- */
if (cpu_has_lasx)
*v |= CPUCFG2_LASX;
@@ -345,24 +341,26 @@ static int kvm_check_cpucfg(int id, u64 val)
switch (id) {
case 2:
- /* CPUCFG2 features checking */
if (!(val & CPUCFG2_LLFTP))
- /* The LLFTP must be set, as guest must has a constant timer */
- ret = -EINVAL;
- else if ((val & CPUCFG2_FP) && (!(val & CPUCFG2_FPSP) || !(val & CPUCFG2_FPDP)))
- /* Single and double float point must both be set when enable FP */
- ret = -EINVAL;
- else if ((val & CPUCFG2_LSX) && !(val & CPUCFG2_FP))
- /* FP should be set when enable LSX */
- ret = -EINVAL;
- else if ((val & CPUCFG2_LASX) && !(val & CPUCFG2_LSX))
- /* LSX, FP should be set when enable LASX, and FP has been checked before. */
- ret = -EINVAL;
- break;
+ /* Guests must have a constant timer */
+ return -EINVAL;
+ if ((val & CPUCFG2_FP) && (!(val & CPUCFG2_FPSP) || !(val & CPUCFG2_FPDP)))
+ /* Single and double float point must both be set when FP is enabled */
+ return -EINVAL;
+ if ((val & CPUCFG2_LSX) && !(val & CPUCFG2_FP))
+ /* LSX architecturally implies FP but val does not satisfy that */
+ return -EINVAL;
+ if ((val & CPUCFG2_LASX) && !(val & CPUCFG2_LSX))
+ /* LASX architecturally implies LSX and FP but val does not satisfy that */
+ return -EINVAL;
+ return 0;
default:
- break;
+ /*
+ * Values for the other CPUCFG IDs are not being further validated
+ * besides the mask check above.
+ */
+ return 0;
}
- return ret;
}
static int kvm_get_one_reg(struct kvm_vcpu *vcpu,
--
2.43.0