iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

KVM: x86: Explicitly track all possibilities for APIC map's logical modes

Browse Source 
Track all possibilities for the optimized APIC map's logical modes
instead of overloading the pseudo-bitmap and treating any "unknown" value
as "invalid".

As documented by the now-stale comment above the mode values, the values
did have meaning when the optimized map was originally added.  That
dependent logical was removed by commit e45115b62f9a ("KVM: x86: use
physical LAPIC array for logical x2APIC"), but the obfuscated behavior
and its comment were left behind.

Opportunistically rename "mode" to "logical_mode", partly to make it
clear that the "disabled" case applies only to the logical map, but also
to prove that there is no lurking code that expects "mode" to be a bitmap.

Functionally, this is a glorified nop.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20230106011306.85230-19-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2023-01-06 01:12:51 +00:00 committed by Paolo Bonzini
parent 6ea567ca00
commit 3536690101
2 changed files with 52 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
arch/x86/include/asm/kvm_host.h
View File

@ -1022,19 +1022,30 @@ struct kvm_arch_memory_slot {
};
/*
* We use as the mode the number of bits allocated in the LDR for the
* logical processor ID. It happens that these are all powers of two.
* This makes it is very easy to detect cases where the APICs are
* configured for multiple modes; in that case, we cannot use the map and
* hence cannot use kvm_irq_delivery_to_apic_fast either.
* Track the mode of the optimized logical map, as the rules for decoding the
* destination vary per mode. Enabling the optimized logical map requires all
* software-enabled local APIs to be in the same mode, each addressable APIC to
* be mapped to only one MDA, and each MDA to map to at most one APIC.
*/
#define KVM_APIC_MODE_XAPIC_CLUSTER 4
#define KVM_APIC_MODE_XAPIC_FLAT 8
#define KVM_APIC_MODE_X2APIC 16
enum kvm_apic_logical_mode {
/* All local APICs are software disabled. */
KVM_APIC_MODE_SW_DISABLED,
/* All software enabled local APICs in xAPIC cluster addressing mode. */
KVM_APIC_MODE_XAPIC_CLUSTER,
/* All software enabled local APICs in xAPIC flat addressing mode. */
KVM_APIC_MODE_XAPIC_FLAT,
/* All software enabled local APICs in x2APIC mode. */
KVM_APIC_MODE_X2APIC,
/*
* Optimized map disabled, e.g. not all local APICs in the same logical
* mode, same logical ID assigned to multiple APICs, etc.
*/
KVM_APIC_MODE_MAP_DISABLED,
};
struct kvm_apic_map {
struct rcu_head rcu;
u8 mode;
enum kvm_apic_logical_mode logical_mode;
u32 max_apic_id;
union {
struct kvm_lapic *xapic_flat_map[8];

40
arch/x86/kvm/lapic.c
View File

@ -168,7 +168,12 @@ static bool kvm_use_posted_timer_interrupt(struct kvm_vcpu *vcpu)
static inline bool kvm_apic_map_get_logical_dest(struct kvm_apic_map *map,
u32 dest_id, struct kvm_lapic ***cluster, u16 *mask) {
switch (map->mode) {
switch (map->logical_mode) {
case KVM_APIC_MODE_SW_DISABLED:
/* Arbitrarily use the flat map so that @cluster isn't NULL. */
*cluster = map->xapic_flat_map;
*mask = 0;
return true;
case KVM_APIC_MODE_X2APIC: {
u32 offset = (dest_id >> 16) * 16;
u32 max_apic_id = map->max_apic_id;
@ -193,8 +198,10 @@ static inline bool kvm_apic_map_get_logical_dest(struct kvm_apic_map *map,
*cluster = map->xapic_cluster_map[(dest_id >> 4) & 0xf];
*mask = dest_id & 0xf;
return true;
case KVM_APIC_MODE_MAP_DISABLED:
return false;
default:
/* Not optimized. */
WARN_ON_ONCE(1);
return false;
}
}
@ -256,10 +263,12 @@ void kvm_recalculate_apic_map(struct kvm *kvm)
goto out;
new->max_apic_id = max_id;
new->logical_mode = KVM_APIC_MODE_SW_DISABLED;
kvm_for_each_vcpu(i, vcpu, kvm) {
struct kvm_lapic *apic = vcpu->arch.apic;
struct kvm_lapic **cluster;
enum kvm_apic_logical_mode logical_mode;
u16 mask;
u32 ldr;
u8 xapic_id;
@ -282,7 +291,8 @@ void kvm_recalculate_apic_map(struct kvm *kvm)
if (!apic_x2apic_mode(apic) && !new->phys_map[xapic_id])
new->phys_map[xapic_id] = apic;
if (!kvm_apic_sw_enabled(apic))
if (new->logical_mode == KVM_APIC_MODE_MAP_DISABLED ||
!kvm_apic_sw_enabled(apic))
continue;
ldr = kvm_lapic_get_reg(apic, APIC_LDR);
@ -290,17 +300,31 @@ void kvm_recalculate_apic_map(struct kvm *kvm)
continue;
if (apic_x2apic_mode(apic)) {
new->mode |= KVM_APIC_MODE_X2APIC;
logical_mode = KVM_APIC_MODE_X2APIC;
} else {
ldr = GET_APIC_LOGICAL_ID(ldr);
if (kvm_lapic_get_reg(apic, APIC_DFR) == APIC_DFR_FLAT)
new->mode |= KVM_APIC_MODE_XAPIC_FLAT;
logical_mode = KVM_APIC_MODE_XAPIC_FLAT;
else
new->mode |= KVM_APIC_MODE_XAPIC_CLUSTER;
logical_mode = KVM_APIC_MODE_XAPIC_CLUSTER;
}
if (!kvm_apic_map_get_logical_dest(new, ldr, &cluster, &mask))
/*
* To optimize logical mode delivery, all software-enabled APICs must
* be configured for the same mode.
*/
if (new->logical_mode == KVM_APIC_MODE_SW_DISABLED) {
new->logical_mode = logical_mode;
} else if (new->logical_mode != logical_mode) {
new->logical_mode = KVM_APIC_MODE_MAP_DISABLED;
continue;
}
if (WARN_ON_ONCE(!kvm_apic_map_get_logical_dest(new, ldr,
&cluster, &mask))) {
new->logical_mode = KVM_APIC_MODE_MAP_DISABLED;
continue;
}
if (mask)
cluster[ffs(mask) - 1] = apic;
@ -953,7 +977,7 @@ static bool kvm_apic_is_broadcast_dest(struct kvm *kvm, struct kvm_lapic **src,
{
if (kvm->arch.x2apic_broadcast_quirk_disabled) {
if ((irq->dest_id == APIC_BROADCAST &&
map->mode != KVM_APIC_MODE_X2APIC))
map->logical_mode != KVM_APIC_MODE_X2APIC))
return true;
if (irq->dest_id == X2APIC_BROADCAST)
return true;