[PATCH v2 16/66] KVM: x86: Encapsulate CPUID entries and metadata in struct

Sean Christopherson
2020-03-03T00:02:09Z

Add a struct to hold the array of CPUID entries and its associated
metadata when handling KVM_GET_SUPPORTED_CPUID. Lookup and provide
the correct entry in do_host_cpuid(), which eliminates the majority of
array indexing shenanigans, e.g. entries[i -1], and generally makes the
code more readable. The last array indexing holdout is kvm_get_cpuid(),
which can't really be avoided without throwing the baby out with the
bathwater.

No functional change intended.

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kvm/cpuid.c | 138 ++++++++++++++++++++++++-------------------
1 file changed, 76 insertions(+), 62 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index d75d539da759..59195de22d8f 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -287,13 +287,21 @@ static __always_inline void cpuid_mask(u32 *word, int wordnum)
*word &= boot_cpu_data.x86_capability[wordnum];
}

-static struct kvm_cpuid_entry2 *do_host_cpuid(struct kvm_cpuid_entry2 *entry,
- int *nent, int maxnent,
+struct kvm_cpuid_array {
+ struct kvm_cpuid_entry2 *entries;
+ const int maxnent;
+ int nent;
+};
+
+static struct kvm_cpuid_entry2 *do_host_cpuid(struct kvm_cpuid_array *array,
u32 function, u32 index)
{
- if (*nent >= maxnent)
+ struct kvm_cpuid_entry2 *entry;
+
+ if (array->nent >= array->maxnent)
return NULL;
- ++*nent;
+
+ entry = &array->entries[array->nent++];

entry->function = function;
entry->index = index;
@@ -325,9 +333,10 @@ static struct kvm_cpuid_entry2 *do_host_cpuid(struct kvm_cpuid_entry2 *entry,
return entry;
}

-static int __do_cpuid_func_emulated(struct kvm_cpuid_entry2 *entry,
- u32 func, int *nent, int maxnent)
+static int __do_cpuid_func_emulated(struct kvm_cpuid_array *array, u32 func)
{
+ struct kvm_cpuid_entry2 *entry = &array->entries[array->nent];
+
entry->function = func;
entry->index = 0;
entry->flags = 0;
@@ -335,17 +344,17 @@ static int __do_cpuid_func_emulated(struct kvm_cpuid_entry2 *entry,
switch (func) {
case 0:
entry->eax = 7;
- ++*nent;
+ ++array->nent;
break;
case 1:
entry->ecx = F(MOVBE);
- ++*nent;
+ ++array->nent;
break;
case 7:
entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
entry->eax = 0;
entry->ecx = F(RDPID);
- ++*nent;
+ ++array->nent;
default:
break;
}
@@ -436,9 +445,9 @@ static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry)
}
}

-static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
- int *nent, int maxnent)
+static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
{
+ struct kvm_cpuid_entry2 *entry;
int r, i, max_idx;
unsigned f_nx = is_efer_nx() ? F(NX) : 0;
#ifdef CONFIG_X86_64
@@ -514,7 +523,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,

r = -E2BIG;

- if (WARN_ON(!do_host_cpuid(entry, nent, maxnent, function, 0)))
+ entry = do_host_cpuid(array, function, 0);
+ if (WARN_ON(!entry))
goto out;

switch (function) {
@@ -539,7 +549,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
entry->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;

for (i = 1, max_idx = entry->eax & 0xff; i < max_idx; ++i) {
- if (!do_host_cpuid(&entry[i], nent, maxnent, function, 0))
+ entry = do_host_cpuid(array, function, 0);
+ if (!entry)
goto out;
}
break;
@@ -550,8 +561,9 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
* Read entries until the cache type in the previous entry is
* zero, i.e. indicates an invalid entry.
*/
- for (i = 1; entry[i - 1].eax & 0x1f; ++i) {
- if (!do_host_cpuid(&entry[i], nent, maxnent, function, i))
+ for (i = 1; entry->eax & 0x1f; ++i) {
+ entry = do_host_cpuid(array, function, i);
+ if (!entry)
goto out;
}
break;
@@ -566,10 +578,11 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
do_cpuid_7_mask(entry);

for (i = 1, max_idx = entry->eax; i <= max_idx; i++) {
- if (!do_host_cpuid(&entry[i], nent, maxnent, function, i))
+ entry = do_host_cpuid(array, function, i);
+ if (!entry)
goto out;

- do_cpuid_7_mask(&entry[i]);
+ do_cpuid_7_mask(entry);
}
break;
case 9:
@@ -610,15 +623,13 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
case 0x1f:
case 0xb:
/*
- * We filled in entry[0] for CPUID(EAX=<function>,
- * ECX=00H) above. If its level type (ECX[15:8]) is
- * zero, then the leaf is unimplemented, and we're
- * done. Otherwise, continue to populate entries
- * until the level type (ECX[15:8]) of the previously
- * added entry is zero.
+ * Populate entries until the level type (ECX[15:8]) of the
+ * previous entry is zero. Note, CPUID EAX.{0x1f,0xb}.0 is
+ * the starting entry, filled by the primary do_host_cpuid().
*/
- for (i = 1; entry[i - 1].ecx & 0xff00; ++i) {
- if (!do_host_cpuid(&entry[i], nent, maxnent, function, i))
+ for (i = 1; entry->ecx & 0xff00; ++i) {
+ entry = do_host_cpuid(array, function, i);
+ if (!entry)
goto out;
}
break;
@@ -633,24 +644,26 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
if (!supported)
break;

- if (!do_host_cpuid(&entry[1], nent, maxnent, function, 1))
+ entry = do_host_cpuid(array, function, 1);
+ if (!entry)
goto out;

- entry[1].eax &= kvm_cpuid_D_1_eax_x86_features;
- cpuid_mask(&entry[1].eax, CPUID_D_1_EAX);
- if (entry[1].eax & (F(XSAVES)|F(XSAVEC)))
- entry[1].ebx = xstate_required_size(supported, true);
+ entry->eax &= kvm_cpuid_D_1_eax_x86_features;
+ cpuid_mask(&entry->eax, CPUID_D_1_EAX);
+ if (entry->eax & (F(XSAVES)|F(XSAVEC)))
+ entry->ebx = xstate_required_size(supported, true);
else
- entry[1].ebx = 0;
+ entry->ebx = 0;
/* Saving XSS controlled state via XSAVES isn't supported. */
- entry[1].ecx = 0;
- entry[1].edx = 0;
+ entry->ecx = 0;
+ entry->edx = 0;

- for (idx = 2, i = 2; idx < 64; ++idx) {
+ for (idx = 2; idx < 64; ++idx) {
if (!(supported & BIT_ULL(idx)))
continue;

- if (!do_host_cpuid(&entry[i], nent, maxnent, function, idx))
+ entry = do_host_cpuid(array, function, idx);
+ if (!entry)
goto out;

/*
@@ -660,14 +673,13 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
* reach this point, and they should have a non-zero
* save state size.
*/
- if (WARN_ON_ONCE(!entry[i].eax || (entry[i].ecx & 1))) {
- --*nent;
+ if (WARN_ON_ONCE(!entry->eax || (entry->ecx & 1))) {
+ --array->nent;
continue;
}

- entry[i].ecx = 0;
- entry[i].edx = 0;
- ++i;
+ entry->ecx = 0;
+ entry->edx = 0;
}
break;
}
@@ -677,7 +689,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
break;

for (i = 1, max_idx = entry->eax; i <= max_idx; ++i) {
- if (!do_host_cpuid(&entry[i], nent, maxnent, function, i))
+ if (!do_host_cpuid(array, function, i))
goto out;
}
break;
@@ -802,22 +814,22 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
return r;
}

-static int do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 func,
- int *nent, int maxnent, unsigned int type)
+static int do_cpuid_func(struct kvm_cpuid_array *array, u32 func,
+ unsigned int type)
{
- if (*nent >= maxnent)
+ if (array->nent >= array->maxnent)
return -E2BIG;

if (type == KVM_GET_EMULATED_CPUID)
- return __do_cpuid_func_emulated(entry, func, nent, maxnent);
+ return __do_cpuid_func_emulated(array, func);

- return __do_cpuid_func(entry, func, nent, maxnent);
+ return __do_cpuid_func(array, func);
}

#define CENTAUR_CPUID_SIGNATURE 0xC0000000

-static int get_cpuid_func(struct kvm_cpuid_entry2 *entries, u32 func,
- int *nent, int maxnent, unsigned int type)
+static int get_cpuid_func(struct kvm_cpuid_array *array, u32 func,
+ unsigned int type)
{
u32 limit;
int r;
@@ -826,16 +838,16 @@ static int get_cpuid_func(struct kvm_cpuid_entry2 *entries, u32 func,
boot_cpu_data.x86_vendor != X86_VENDOR_CENTAUR)
return 0;

- r = do_cpuid_func(&entries[*nent], func, nent, maxnent, type);
+ r = do_cpuid_func(array, func, type);
if (r)
return r;

- limit = entries[*nent - 1].eax;
+ limit = array->entries[array->nent - 1].eax;
for (func = func + 1; func <= limit; ++func) {
- if (*nent >= maxnent)
+ if (array->nent >= array->maxnent)
return -E2BIG;

- r = do_cpuid_func(&entries[*nent], func, nent, maxnent, type);
+ r = do_cpuid_func(array, func, type);
if (r)
break;
}
@@ -878,8 +890,11 @@ int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
0, 0x80000000, CENTAUR_CPUID_SIGNATURE, KVM_CPUID_SIGNATURE,
};

- struct kvm_cpuid_entry2 *cpuid_entries;
- int nent = 0, r, i;
+ struct kvm_cpuid_array array = {
+ .nent = 0,
+ .maxnent = cpuid->nent,
+ };
+ int r, i;

if (cpuid->nent < 1)
return -E2BIG;
@@ -889,25 +904,24 @@ int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
if (sanity_check_entries(entries, cpuid->nent, type))
return -EINVAL;

- cpuid_entries = vzalloc(array_size(sizeof(struct kvm_cpuid_entry2),
+ array.entries = vzalloc(array_size(sizeof(struct kvm_cpuid_entry2),
cpuid->nent));
- if (!cpuid_entries)
+ if (!array.entries)
return -ENOMEM;

for (i = 0; i < ARRAY_SIZE(funcs); i++) {
- r = get_cpuid_func(cpuid_entries, funcs[i], &nent, cpuid->nent,
- type);
+ r = get_cpuid_func(&array, funcs[i], type);
if (r)
goto out_free;
}
- cpuid->nent = nent;
+ cpuid->nent = array.nent;

- if (copy_to_user(entries, cpuid_entries,
- nent * sizeof(struct kvm_cpuid_entry2)))
+ if (copy_to_user(entries, array.entries,
+ array.nent * sizeof(struct kvm_cpuid_entry2)))
r = -EFAULT;

out_free:
- vfree(cpuid_entries);
+ vfree(array.entries);
return r;
}

--
2.24.1