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Date: Fri, 30 Jan 2015 10:18:20 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: Radim Krčmář <rkrcmar@...hat.com>,
linux-kernel@...r.kernel.org
CC: kvm@...r.kernel.org, Nadav Amit <namit@...technion.ac.il>,
Gleb Natapov <gleb@...nel.org>
Subject: Re: [PATCH 8/8] KVM: x86: simplify kvm_apic_map
On 29/01/2015 22:48, Radim Krčmář wrote:
> recalculate_apic_map() uses two passes over all VCPUs. This is a relic
> from time when we selected a global mode in the first pass and set up
> the optimized table in the second pass (to have a consistent mode).
>
> Recent changes made mixed mode unoptimized and we can do it in one pass.
> Format of logical MDA is a function of the mode, so we encode it in
> apic_logical_id() and drop obsoleted variables from the struct.
>
> Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
> ---
> arch/x86/include/asm/kvm_host.h | 3 --
> arch/x86/kvm/lapic.c | 78 ++++++++++-------------------------------
> arch/x86/kvm/lapic.h | 29 ++++++++-------
> 3 files changed, 36 insertions(+), 74 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index fec3188cabbb..14b6b0fd17b1 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -555,9 +555,6 @@ struct kvm_arch_memory_slot {
> struct kvm_apic_map {
> struct rcu_head rcu;
> u8 mode;
> - u8 ldr_bits;
> - /* fields bellow are used to decode ldr values in different modes */
> - u32 cid_shift, cid_mask, lid_mask;
> struct kvm_lapic *phys_map[256];
> /* first index is cluster id second is cpu id in a cluster */
> struct kvm_lapic *logical_map[16][16];
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 621d9df6ac63..f74557791a77 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -146,49 +146,6 @@ static void recalculate_apic_map(struct kvm *kvm)
> if (!new)
> goto out;
>
> - new->ldr_bits = 8;
> - /* flat mode is default */
> - new->cid_shift = 8;
> - new->cid_mask = 0;
> - new->lid_mask = 0xff;
> -
> - kvm_for_each_vcpu(i, vcpu, kvm) {
> - struct kvm_lapic *apic = vcpu->arch.apic;
> -
> - if (!kvm_apic_present(vcpu))
> - continue;
> -
> - if (apic_x2apic_mode(apic)) {
> - new->ldr_bits = 32;
> - new->cid_shift = 16;
> - new->cid_mask = new->lid_mask = 0xffff;
> - new->mode |= KVM_APIC_MODE_X2APIC;
> - } else if (kvm_apic_get_reg(apic, APIC_LDR)) {
> - if (kvm_apic_get_reg(apic, APIC_DFR) ==
> - APIC_DFR_CLUSTER) {
> - new->cid_shift = 4;
> - new->cid_mask = 0xf;
> - new->lid_mask = 0xf;
> - new->mode |= KVM_APIC_MODE_XAPIC_CLUSTER;
> - } else {
> - new->cid_shift = 8;
> - new->cid_mask = 0;
> - new->lid_mask = 0xff;
> - new->mode |= KVM_APIC_MODE_XAPIC_FLAT;
> - }
> - }
> -
> - /*
> - * All APICs have to be configured in the same mode by an OS.
> - * We take advatage of this while building logical id loockup
> - * table. After reset APICs are in software disabled mode, so if
> - * we find apic with different setting we assume this is the mode
> - * OS wants all apics to be in; build lookup table accordingly.
> - */
> - if (kvm_apic_sw_enabled(apic))
> - break;
> - }
> -
> kvm_for_each_vcpu(i, vcpu, kvm) {
> struct kvm_lapic *apic = vcpu->arch.apic;
> u16 cid, lid;
> @@ -198,17 +155,22 @@ static void recalculate_apic_map(struct kvm *kvm)
> continue;
>
> aid = kvm_apic_id(apic);
> - ldr = kvm_apic_get_reg(apic, APIC_LDR);
> - cid = apic_cluster_id(new, ldr);
> - lid = apic_logical_id(new, ldr);
> -
> if (aid < ARRAY_SIZE(new->phys_map))
> new->phys_map[aid] = apic;
>
> - /* The logical map is definitely wrong if we have multiple
> - * modes at the same time. Physical is still right though.
> - */
> - if (hweight8(new->mode) != 1)
> + ldr = kvm_apic_get_reg(apic, APIC_LDR);
> +
> + if (apic_x2apic_mode(apic)) {
> + new->mode |= KVM_APIC_MODE_X2APIC;
> + } else if (ldr) {
> + ldr = GET_APIC_LOGICAL_ID(ldr);
> + if (kvm_apic_get_reg(apic, APIC_DFR) == APIC_DFR_FLAT)
> + new->mode |= KVM_APIC_MODE_XAPIC_FLAT;
> + else
> + new->mode |= KVM_APIC_MODE_XAPIC_CLUSTER;
> + }
> +
> + if (!apic_logical_id(new, ldr, &cid, &lid))
> continue;
>
> if (lid && cid < ARRAY_SIZE(new->logical_map))
> @@ -724,22 +686,20 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
>
> dst = &map->phys_map[irq->dest_id];
> } else {
> - u32 mda = irq->dest_id << (32 - map->ldr_bits);
> - u16 cid = apic_cluster_id(map, mda);
> + u16 cid;
>
> - if (cid >= ARRAY_SIZE(map->logical_map))
> - goto out;
> -
> - if (hweight8(map->mode) != 1) {
> + if (!apic_logical_id(map, irq->dest_id, &cid, (u16 *)&bitmap))
> + {
> /* Not deliverable with optimized map. */
> ret = false;
> goto out;
> }
>
> + if (cid >= ARRAY_SIZE(map->logical_map))
> + goto out;
> +
> dst = map->logical_map[cid];
>
> - bitmap = apic_logical_id(map, mda);
> -
> if (irq->delivery_mode == APIC_DM_LOWEST) {
> int l = -1;
> for_each_set_bit(i, &bitmap, 16) {
> diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> index fd0197a93862..320716e301a8 100644
> --- a/arch/x86/kvm/lapic.h
> +++ b/arch/x86/kvm/lapic.h
> @@ -151,19 +151,24 @@ static inline bool kvm_apic_vid_enabled(struct kvm *kvm)
> return kvm_x86_ops->vm_has_apicv(kvm);
> }
>
> -static inline u16 apic_cluster_id(struct kvm_apic_map *map, u32 ldr)
> +static inline bool
> +apic_logical_id(struct kvm_apic_map *map, u32 ldr, u16 *cid, u16 *lid)
> {
> - u16 cid;
> - ldr >>= 32 - map->ldr_bits;
> - cid = (ldr >> map->cid_shift) & map->cid_mask;
> -
> - return cid;
> -}
> -
> -static inline u16 apic_logical_id(struct kvm_apic_map *map, u32 ldr)
> -{
> - ldr >>= (32 - map->ldr_bits);
> - return ldr & map->lid_mask;
> + switch (map->mode) {
> + case KVM_APIC_MODE_XAPIC_FLAT:
> + *cid = 0;
> + *lid = ldr & 0xff;
> + return true;
> + case KVM_APIC_MODE_XAPIC_CLUSTER:
> + *cid = (ldr >> 4) & 0xf;
> + *lid = ldr & 0xf;
> + return true;
> + case KVM_APIC_MODE_X2APIC:
> + *cid = ldr >> 16;
> + *lid = ldr & 0xffff;
> + return true;
> + }
We need some optimization here. You can make the defines equal to the
size of the lid: CLUSTER = 1 << 3, FLAT = 1 << 2, X2APIC = 1 << 4:
BUILD_BUG_ON(...FLAT != 4);
BUILD_BUG_ON(...CLUSTER != 8);
BUILD_BUG_ON(...X2APIC != 16);
lid_bits = mode;
cid_bits = mode & (16 | 4);
lid_mask = (1 << lid_bits) - 1;
cid_mask = (1 << cid_bits) - 1;
*cid = (ldr >> lid_bits) & cid_mask;
*lid = ldr & lid_mask;
Please move this to lapic.c since you are at it.
Paolo
> + return false;
> }
>
> static inline bool kvm_apic_has_events(struct kvm_vcpu *vcpu)
>
--
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