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Message-ID: <CAKgT0Udqm2qNQ1+mPkx7vx=c2a7Hjq92fKM30041e1kU47bcHA@mail.gmail.com>
Date: Mon, 3 Jun 2019 11:34:27 -0700
From: Alexander Duyck <alexander.duyck@...il.com>
To: Nitesh Narayan Lal <nitesh@...hat.com>
Cc: kvm list <kvm@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
linux-mm <linux-mm@...ck.org>,
Paolo Bonzini <pbonzini@...hat.com>, lcapitulino@...hat.com,
pagupta@...hat.com, wei.w.wang@...el.com,
Yang Zhang <yang.zhang.wz@...il.com>,
Rik van Riel <riel@...riel.com>,
David Hildenbrand <david@...hat.com>,
"Michael S. Tsirkin" <mst@...hat.com>, dodgen@...gle.com,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
dhildenb@...hat.com, Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [QEMU PATCH] KVM: Support for page hinting
On Mon, Jun 3, 2019 at 10:04 AM Nitesh Narayan Lal <nitesh@...hat.com> wrote:
>
> Enables QEMU to call madvise on the pages which are reported
> by the guest kernel.
>
> Signed-off-by: Nitesh Narayan Lal <nitesh@...hat.com>
What commit-id is this meant to apply on top of? I can't apply this to
the latest development version of QEMU.
> ---
> hw/virtio/trace-events | 1 +
> hw/virtio/virtio-balloon.c | 85 +++++++++++++++++++
> include/hw/virtio/virtio-balloon.h | 2 +-
> include/qemu/osdep.h | 7 ++
> .../standard-headers/linux/virtio_balloon.h | 1 +
> 5 files changed, 95 insertions(+), 1 deletion(-)
>
> diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> index 07bcbe9e85..015565785c 100644
> --- a/hw/virtio/trace-events
> +++ b/hw/virtio/trace-events
> @@ -46,3 +46,4 @@ virtio_balloon_handle_output(const char *name, uint64_t gpa) "section name: %s g
> virtio_balloon_get_config(uint32_t num_pages, uint32_t actual) "num_pages: %d actual: %d"
> virtio_balloon_set_config(uint32_t actual, uint32_t oldactual) "actual: %d oldactual: %d"
> virtio_balloon_to_target(uint64_t target, uint32_t num_pages) "balloon target: 0x%"PRIx64" num_pages: %d"
> +virtio_balloon_hinting_request(unsigned long pfn, unsigned int num_pages) "Guest page hinting request: %lu size: %d"
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> index a12677d4d5..cbb630279c 100644
> --- a/hw/virtio/virtio-balloon.c
> +++ b/hw/virtio/virtio-balloon.c
> @@ -33,6 +33,13 @@
>
> #define BALLOON_PAGE_SIZE (1 << VIRTIO_BALLOON_PFN_SHIFT)
>
> +struct guest_pages {
> + uint64_t phys_addr;
> + uint32_t len;
> +};
> +
Any reason for matching up 64b addr w/ 32b size? The way I see it you
would be be better off going with either 64b for both or 32b for both.
I opted for the 32b approach in my case since there was already code
in place for doing the PFN shift anyway in the standard virtio_balloon
code path.
> +void page_hinting_request(uint64_t addr, uint32_t len);
> +
> static void balloon_page(void *addr, int deflate)
> {
> if (!qemu_balloon_is_inhibited()) {
> @@ -207,6 +214,80 @@ static void balloon_stats_set_poll_interval(Object *obj, Visitor *v,
> balloon_stats_change_timer(s, 0);
> }
>
> +static void *gpa2hva(MemoryRegion **p_mr, hwaddr addr, Error **errp)
> +{
> + MemoryRegionSection mrs = memory_region_find(get_system_memory(),
> + addr, 1);
> +
> + if (!mrs.mr) {
> + error_setg(errp, "No memory is mapped at address 0x%" HWADDR_PRIx, addr);
> + return NULL;
> + }
> +
> + if (!memory_region_is_ram(mrs.mr) && !memory_region_is_romd(mrs.mr)) {
> + error_setg(errp, "Memory at address 0x%" HWADDR_PRIx "is not RAM", addr);
> + memory_region_unref(mrs.mr);
> + return NULL;
> + }
> +
> + *p_mr = mrs.mr;
> + return qemu_map_ram_ptr(mrs.mr->ram_block, mrs.offset_within_region);
> +}
> +
> +void page_hinting_request(uint64_t addr, uint32_t len)
> +{
> + Error *local_err = NULL;
> + MemoryRegion *mr = NULL;
> + int ret = 0;
> + struct guest_pages *guest_obj;
> + int i = 0;
> + void *hvaddr_to_free;
> + uint64_t gpaddr_to_free;
> + void * temp_addr = gpa2hva(&mr, addr, &local_err);
> +
> + if (local_err) {
> + error_report_err(local_err);
> + return;
> + }
> + guest_obj = temp_addr;
> + while (i < len) {
> + gpaddr_to_free = guest_obj[i].phys_addr;
> + trace_virtio_balloon_hinting_request(gpaddr_to_free,guest_obj[i].len);
> + hvaddr_to_free = gpa2hva(&mr, gpaddr_to_free, &local_err);
> + if (local_err) {
> + error_report_err(local_err);
> + return;
> + }
> + ret = qemu_madvise((void *)hvaddr_to_free, guest_obj[i].len, QEMU_MADV_FREE);
> + if (ret == -1)
> + printf("\n%d:%s Error: Madvise failed with error:%d\n", __LINE__, __func__, ret);
> + i++;
> + }
> +}
> +
Have we made any determination yet on the MADV_FREE vs MADV_DONT_NEED?
My preference would be to have this code just reuse the existing
balloon code as I did in my patch set. Then we can avoid the need to
have multiple types in use. We could just have the balloon use the
same as the hint.
> +static void virtio_balloon_page_hinting(VirtIODevice *vdev, VirtQueue *vq)
> +{
> + VirtQueueElement *elem = NULL;
> + uint64_t temp_addr;
> + uint32_t temp_len;
> + size_t size, t_size = 0;
> +
> + elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
> + if (!elem) {
> + printf("\npop error\n");
> + return;
> + }
> + size = iov_to_buf(elem->out_sg, elem->out_num, 0, &temp_addr, sizeof(temp_addr));
> + t_size += size;
> + size = iov_to_buf(elem->out_sg, elem->out_num, 8, &temp_len, sizeof(temp_len));
> + t_size += size;
> + if (!qemu_balloon_is_inhibited())
> + page_hinting_request(temp_addr, temp_len);
> + virtqueue_push(vq, elem, t_size);
> + virtio_notify(vdev, vq);
> + g_free(elem);
> +}
> +
If you are doing a u64 addr, and a u32 len, does that mean you are
having to use a packed array between the guest and the host? This
would be another good reason to have both settle on either u64 or u32.
> static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
> {
> VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
> @@ -376,6 +457,7 @@ static uint64_t virtio_balloon_get_features(VirtIODevice *vdev, uint64_t f,
> VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
> f |= dev->host_features;
> virtio_add_feature(&f, VIRTIO_BALLOON_F_STATS_VQ);
> + virtio_add_feature(&f, VIRTIO_BALLOON_F_HINTING);
> return f;
> }
>
> @@ -445,6 +527,7 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
> s->ivq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
> s->dvq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
> s->svq = virtio_add_queue(vdev, 128, virtio_balloon_receive_stats);
> + s->hvq = virtio_add_queue(vdev, 128, virtio_balloon_page_hinting);
>
> reset_stats(s);
> }
> @@ -488,6 +571,8 @@ static void virtio_balloon_instance_init(Object *obj)
>
> object_property_add(obj, "guest-stats", "guest statistics",
> balloon_stats_get_all, NULL, NULL, s, NULL);
> + object_property_add(obj, "guest-page-hinting", "guest page hinting",
> + NULL, NULL, NULL, s, NULL);
>
> object_property_add(obj, "guest-stats-polling-interval", "int",
> balloon_stats_get_poll_interval,
> diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h
> index e0df3528c8..774498a6ca 100644
> --- a/include/hw/virtio/virtio-balloon.h
> +++ b/include/hw/virtio/virtio-balloon.h
> @@ -32,7 +32,7 @@ typedef struct virtio_balloon_stat_modern {
>
> typedef struct VirtIOBalloon {
> VirtIODevice parent_obj;
> - VirtQueue *ivq, *dvq, *svq;
> + VirtQueue *ivq, *dvq, *svq, *hvq;
> uint32_t num_pages;
> uint32_t actual;
> uint64_t stats[VIRTIO_BALLOON_S_NR];
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 840af09cb0..4d632933a9 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -360,6 +360,11 @@ void qemu_anon_ram_free(void *ptr, size_t size);
> #else
> #define QEMU_MADV_REMOVE QEMU_MADV_INVALID
> #endif
> +#ifdef MADV_FREE
> +#define QEMU_MADV_FREE MADV_FREE
> +#else
> +#define QEMU_MADV_FREE QEMU_MADV_INVALID
> +#endif
>
> #elif defined(CONFIG_POSIX_MADVISE)
>
> @@ -373,6 +378,7 @@ void qemu_anon_ram_free(void *ptr, size_t size);
> #define QEMU_MADV_HUGEPAGE QEMU_MADV_INVALID
> #define QEMU_MADV_NOHUGEPAGE QEMU_MADV_INVALID
> #define QEMU_MADV_REMOVE QEMU_MADV_INVALID
> +#define QEMU_MADV_FREE QEMU_MADV_INVALID
>
> #else /* no-op */
>
> @@ -386,6 +392,7 @@ void qemu_anon_ram_free(void *ptr, size_t size);
> #define QEMU_MADV_HUGEPAGE QEMU_MADV_INVALID
> #define QEMU_MADV_NOHUGEPAGE QEMU_MADV_INVALID
> #define QEMU_MADV_REMOVE QEMU_MADV_INVALID
> +#define QEMU_MADV_FREE QEMU_MADV_INVALID
>
> #endif
>
> diff --git a/include/standard-headers/linux/virtio_balloon.h b/include/standard-headers/linux/virtio_balloon.h
> index 4dbb7dc6c0..f50c0d95ea 100644
> --- a/include/standard-headers/linux/virtio_balloon.h
> +++ b/include/standard-headers/linux/virtio_balloon.h
> @@ -34,6 +34,7 @@
> #define VIRTIO_BALLOON_F_MUST_TELL_HOST 0 /* Tell before reclaiming pages */
> #define VIRTIO_BALLOON_F_STATS_VQ 1 /* Memory Stats virtqueue */
> #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM 2 /* Deflate balloon on OOM */
> +#define VIRTIO_BALLOON_F_HINTING 5 /* Page hinting virtqueue */
So this is obviously built against an old version of QEMU, the latest
values for this include:
#define VIRTIO_BALLOON_F_FREE_PAGE_HINT 3 /* VQ to report free pages */
#define VIRTIO_BALLOON_F_PAGE_POISON 4 /* Guest is using page poisoning */
I wonder if we shouldn't look for a term other than "HINT" since there
is already the code around providing hints to migration.
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