From 6ad18fba05228fb1d47cdbc0339fe8b3fca1ca26 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Mon, 11 Aug 2008 10:01:49 -0700 Subject: KVM: Reduce stack usage in kvm_pv_mmu_op() We're in a hot path. We can't use kmalloc() because it might impact performance. So, we just stick the buffer that we need into the kvm_vcpu_arch structure. This is used very often, so it is not really a waste. We also have to move the buffer structure's definition to the arch-specific x86 kvm header. Signed-off-by: Dave Hansen Signed-off-by: Avi Kivity --- arch/x86/kvm/mmu.c | 23 ++++++++--------------- 1 file changed, 8 insertions(+), 15 deletions(-) (limited to 'arch/x86/kvm/mmu.c') diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index c3afbfe6b0c..171bcea1be2 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -135,13 +135,6 @@ module_param(dbg, bool, 0644); #define ACC_USER_MASK PT_USER_MASK #define ACC_ALL (ACC_EXEC_MASK | ACC_WRITE_MASK | ACC_USER_MASK) -struct kvm_pv_mmu_op_buffer { - void *ptr; - unsigned len; - unsigned processed; - char buf[512] __aligned(sizeof(long)); -}; - struct kvm_rmap_desc { u64 *shadow_ptes[RMAP_EXT]; struct kvm_rmap_desc *more; @@ -2292,18 +2285,18 @@ int kvm_pv_mmu_op(struct kvm_vcpu *vcpu, unsigned long bytes, gpa_t addr, unsigned long *ret) { int r; - struct kvm_pv_mmu_op_buffer buffer; + struct kvm_pv_mmu_op_buffer *buffer = &vcpu->arch.mmu_op_buffer; - buffer.ptr = buffer.buf; - buffer.len = min_t(unsigned long, bytes, sizeof buffer.buf); - buffer.processed = 0; + buffer->ptr = buffer->buf; + buffer->len = min_t(unsigned long, bytes, sizeof buffer->buf); + buffer->processed = 0; - r = kvm_read_guest(vcpu->kvm, addr, buffer.buf, buffer.len); + r = kvm_read_guest(vcpu->kvm, addr, buffer->buf, buffer->len); if (r) goto out; - while (buffer.len) { - r = kvm_pv_mmu_op_one(vcpu, &buffer); + while (buffer->len) { + r = kvm_pv_mmu_op_one(vcpu, buffer); if (r < 0) goto out; if (r == 0) @@ -2312,7 +2305,7 @@ int kvm_pv_mmu_op(struct kvm_vcpu *vcpu, unsigned long bytes, r = 1; out: - *ret = buffer.processed; + *ret = buffer->processed; return r; } -- cgit v1.2.3-70-g09d2