From 7d765ce07eff78ab78d09d4acaa3aecb71e322a4 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Tue, 15 Sep 2015 14:41:57 +0800 Subject: [PATCH] kvm: fix zero length mmio searching [ Upstream commit 8f4216c7d28976f7ec1b2bcbfa0a9f787133c45e ] Currently, if we had a zero length mmio eventfd assigned on KVM_MMIO_BUS. It will never be found by kvm_io_bus_cmp() since it always compares the kvm_io_range() with the length that guest wrote. This will cause e.g for vhost, kick will be trapped by qemu userspace instead of vhost. Fixing this by using zero length if an iodevice is zero length. Cc: stable@vger.kernel.org Cc: Gleb Natapov Cc: Paolo Bonzini Signed-off-by: Jason Wang Reviewed-by: Cornelia Huck Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- virt/kvm/kvm_main.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 4e52bb926374..329c3c91bb68 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2875,10 +2875,25 @@ static void kvm_io_bus_destroy(struct kvm_io_bus *bus) static inline int kvm_io_bus_cmp(const struct kvm_io_range *r1, const struct kvm_io_range *r2) { - if (r1->addr < r2->addr) + gpa_t addr1 = r1->addr; + gpa_t addr2 = r2->addr; + + if (addr1 < addr2) return -1; - if (r1->addr + r1->len > r2->addr + r2->len) + + /* If r2->len == 0, match the exact address. If r2->len != 0, + * accept any overlapping write. Any order is acceptable for + * overlapping ranges, because kvm_io_bus_get_first_dev ensures + * we process all of them. + */ + if (r2->len) { + addr1 += r1->len; + addr2 += r2->len; + } + + if (addr1 > addr2) return 1; + return 0; }