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KVM x86 fixes and a selftest fix for 6.17-rcN

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- Use array_index_nospec() to sanitize the target vCPU ID when handling PV
    IPIs and yields as the ID is guest-controlled.
 
  - Drop a superfluous cpumask_empty() check when reclaiming SEV memory, as
    the common case, by far, is that at least one CPU will have entered the
    VM, and wbnoinvd_on_cpus_mask() will naturally handle the rare case where
    the set of have_run_cpus is empty.
 
  - Rename the is_signed_type() macro in kselftest_harness.h to is_signed_var()
    to fix a collision with linux/overflow.h.  The collision generates compiler
    warnings due to the two macros having different implementations.
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Merge tag 'kvm-x86-fixes-6.17-rc7' of https://github.com/kvm-x86/linux into HEAD

KVM x86 fixes and a selftest fix for 6.17-rcN

 - Use array_index_nospec() to sanitize the target vCPU ID when handling PV
   IPIs and yields as the ID is guest-controlled.

 - Drop a superfluous cpumask_empty() check when reclaiming SEV memory, as
   the common case, by far, is that at least one CPU will have entered the
   VM, and wbnoinvd_on_cpus_mask() will naturally handle the rare case where
   the set of have_run_cpus is empty.

 - Rename the is_signed_type() macro in kselftest_harness.h to is_signed_var()
   to fix a collision with linux/overflow.h.  The collision generates compiler
   warnings due to the two macros having different implementations.
This commit is contained in:
Paolo Bonzini 2025-08-27 04:18:01 -04:00
commit 22b2ca023f
4 changed files with 12 additions and 11 deletions
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2
arch/x86/kvm/lapic.c
View File

@ -810,6 +810,8 @@ static int __pv_send_ipi(unsigned long *ipi_bitmap, struct kvm_apic_map *map,
if (min > map->max_apic_id)
return 0;
min = array_index_nospec(min, map->max_apic_id + 1);
for_each_set_bit(i, ipi_bitmap,
min((u32)BITS_PER_LONG, (map->max_apic_id - min + 1))) {
if (map->phys_map[min + i]) {

10
arch/x86/kvm/svm/sev.c
View File

@ -718,13 +718,6 @@ static void sev_clflush_pages(struct page *pages[], unsigned long npages)
static void sev_writeback_caches(struct kvm *kvm)
{
/*
* Note, the caller is responsible for ensuring correctness if the mask
* can be modified, e.g. if a CPU could be doing VMRUN.
*/
if (cpumask_empty(to_kvm_sev_info(kvm)->have_run_cpus))
return;
/*
* Ensure that all dirty guest tagged cache entries are written back
* before releasing the pages back to the system for use. CLFLUSH will
@ -739,6 +732,9 @@ static void sev_writeback_caches(struct kvm *kvm)
* serializing multiple calls and having responding CPUs (to the IPI)
* mark themselves as still running if they are running (or about to
* run) a vCPU for the VM.
*
* Note, the caller is responsible for ensuring correctness if the mask
* can be modified, e.g. if a CPU could be doing VMRUN.
*/
wbnoinvd_on_cpus_mask(to_kvm_sev_info(kvm)->have_run_cpus);
}

7
arch/x86/kvm/x86.c
View File

@ -9908,8 +9908,11 @@ static void kvm_sched_yield(struct kvm_vcpu *vcpu, unsigned long dest_id)
rcu_read_lock();
map = rcu_dereference(vcpu->kvm->arch.apic_map);
if (likely(map) && dest_id <= map->max_apic_id && map->phys_map[dest_id])
target = map->phys_map[dest_id]->vcpu;
if (likely(map) && dest_id <= map->max_apic_id) {
dest_id = array_index_nospec(dest_id, map->max_apic_id + 1);
if (map->phys_map[dest_id])
target = map->phys_map[dest_id]->vcpu;
}
rcu_read_unlock();

4
tools/testing/selftests/kselftest_harness.h
View File

@ -751,7 +751,7 @@
for (; _metadata->trigger; _metadata->trigger = \
__bail(_assert, _metadata))
#define is_signed_type(var) (!!(((__typeof__(var))(-1)) < (__typeof__(var))1))
#define is_signed_var(var) (!!(((__typeof__(var))(-1)) < (__typeof__(var))1))
#define __EXPECT(_expected, _expected_str, _seen, _seen_str, _t, _assert) do { \
/* Avoid multiple evaluation of the cases */ \
@ -759,7 +759,7 @@
__typeof__(_seen) __seen = (_seen); \
if (!(__exp _t __seen)) { \
/* Report with actual signedness to avoid weird output. */ \
switch (is_signed_type(__exp) * 2 + is_signed_type(__seen)) { \
switch (is_signed_var(__exp) * 2 + is_signed_var(__seen)) { \
case 0: { \
uintmax_t __exp_print = (uintmax_t)__exp; \
uintmax_t __seen_print = (uintmax_t)__seen; \