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Date: Thu, 15 Mar 2012 12:54:00 -0400
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: Akshay Karle <akshay.a.karle@...il.com>
Cc: linux-kernel@...r.kernel.org,
Dan Magenheimer <dan.magenheimer@...cle.com>,
kvm@...r.kernel.org, ashu tripathi <er.ashutripathi@...il.com>,
nishant gulhane <nishant.s.gulhane@...il.com>,
Shreyas Mahure <shreyas.mahure@...il.com>,
amarmore2006 <amarmore2006@...il.com>,
mahesh mohan <mahesh6490@...il.com>
Subject: Re: [RFC 1/2] kvm: host-side changes for tmem on KVM
On Thu, Mar 08, 2012 at 10:24:08PM +0530, Akshay Karle wrote:
> From: Akshay Karle <akshay.a.karle@...il.com>
> Subject: [RFC 1/2] kvm: host-side changes for tmem on KVM
>
> Working at host:
> Once the guest exits to the kvm host, the host determines that the guest exited
> to perform some tmem operation(done at kvm_emulate_hypercall)and then
> we use zcache to implement this required operations(performed by kvm_pv_tmem_op).
Do you need any modifications to the Kconfig file to reflect the KVM dependency?
>
> ---
> Diffstat for host patch:
> arch/x86/include/asm/kvm_host.h | 1
> arch/x86/kvm/x86.c | 4 +
> drivers/staging/zcache/zcache-main.c | 98 ++++++++++++++++++++++++++++++++---
> 3 files changed, 95 insertions(+), 8 deletions(-)
>
> diff -Napur vanilla/linux-3.1.5/arch/x86/include/asm/kvm_host.h linux-3.1.5//arch/x86/include/asm/kvm_host.h
> --- vanilla/linux-3.1.5/arch/x86/include/asm/kvm_host.h 2011-12-09 22:27:05.000000000 +0530
> +++ linux-3.1.5//arch/x86/include/asm/kvm_host.h 2012-03-05 14:09:41.648006153 +0530
> @@ -668,6 +668,7 @@ int emulator_write_phys(struct kvm_vcpu
> const void *val, int bytes);
> int kvm_pv_mmu_op(struct kvm_vcpu *vcpu, unsigned long bytes,
> gpa_t addr, unsigned long *ret);
> +int kvm_pv_tmem_op(struct kvm_vcpu *vcpu, gpa_t addr, unsigned long *ret);
> u8 kvm_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn);
>
> extern bool tdp_enabled;
> diff -Napur vanilla/linux-3.1.5/arch/x86/kvm/x86.c linux-3.1.5//arch/x86/kvm/x86.c
> --- vanilla/linux-3.1.5/arch/x86/kvm/x86.c 2011-12-09 22:27:05.000000000 +0530
> +++ linux-3.1.5//arch/x86/kvm/x86.c 2012-03-05 14:09:41.652006083 +0530
> @@ -5267,6 +5267,10 @@ int kvm_emulate_hypercall(struct kvm_vcp
> case KVM_HC_MMU_OP:
> r = kvm_pv_mmu_op(vcpu, a0, hc_gpa(vcpu, a1, a2), &ret);
> break;
> + case KVM_HC_TMEM:
> + r = kvm_pv_tmem_op(vcpu, a0, &ret);
> + ret = ret - 1000;
That is rather odd. Why the subtraction of 1000?
> + break;
> default:
> ret = -KVM_ENOSYS;
> break;
> diff -Napur vanilla/linux-3.1.5/drivers/staging/zcache/zcache-main.c linux-3.1.5//drivers/staging/zcache/zcache-main.c
> --- vanilla/linux-3.1.5/drivers/staging/zcache/zcache-main.c 2011-12-09 22:27:05.000000000 +0530
> +++ linux-3.1.5//drivers/staging/zcache/zcache-main.c 2012-03-05 14:10:31.264006031 +0530
> @@ -30,6 +30,7 @@
> #include <linux/atomic.h>
> #include <linux/math64.h>
> #include "tmem.h"
> +#include "kvm-tmem.h"
>
> #include "../zram/xvmalloc.h" /* if built in drivers/staging */
>
> @@ -669,7 +670,6 @@ static struct zv_hdr *zv_create(struct x
> int chunks = (alloc_size + (CHUNK_SIZE - 1)) >> CHUNK_SHIFT;
> int ret;
>
> - BUG_ON(!irqs_disabled());
Can you explain why?
> BUG_ON(chunks >= NCHUNKS);
> ret = xv_malloc(xvpool, alloc_size,
> &page, &offset, ZCACHE_GFP_MASK);
> @@ -1313,7 +1313,6 @@ static int zcache_compress(struct page *
> unsigned char *wmem = __get_cpu_var(zcache_workmem);
> char *from_va;
>
> - BUG_ON(!irqs_disabled());
> if (unlikely(dmem == NULL || wmem == NULL))
> goto out; /* no buffer, so can't compress */
> from_va = kmap_atomic(from, KM_USER0);
> @@ -1533,7 +1532,6 @@ static int zcache_put_page(int cli_id, i
> struct tmem_pool *pool;
> int ret = -1;
>
> - BUG_ON(!irqs_disabled());
> pool = zcache_get_pool_by_id(cli_id, pool_id);
> if (unlikely(pool == NULL))
> goto out;
> @@ -1898,6 +1896,67 @@ struct frontswap_ops zcache_frontswap_re
> #endif
>
> /*
> + * tmem op to support tmem in kvm guests
> + */
> +
> +int kvm_pv_tmem_op(struct kvm_vcpu *vcpu, gpa_t addr, unsigned long *ret)
> +{
> + struct tmem_ops op;
> + struct tmem_oid oid;
> + uint64_t pfn;
> + struct page *page;
> + int r;
> +
> + r = kvm_read_guest(vcpu->kvm, addr, &op, sizeof(op));
> + if (r < 0)
> + return r;
> +
> + switch (op.cmd) {
> + case TMEM_NEW_POOL:
> + *ret = zcache_new_pool(op.u.new.cli_id, op.u.new.flags);
> + break;
> + case TMEM_DESTROY_POOL:
> + *ret = zcache_destroy_pool(op.u.gen.cli_id, op.pool_id);
> + break;
> + case TMEM_NEW_PAGE:
> + break;
> + case TMEM_PUT_PAGE:
> + pfn = gfn_to_pfn(vcpu->kvm, op.u.gen.pfn);
> + page = pfn_to_page(pfn);
> + oid.oid[0] = op.u.gen.oid[0];
> + oid.oid[1] = op.u.gen.oid[1];
> + oid.oid[2] = op.u.gen.oid[2];
> + VM_BUG_ON(!PageLocked(page));
> + *ret = zcache_put_page(op.u.gen.cli_id, op.pool_id,
> + &oid, op.u.gen.index, page);
> + break;
> + case TMEM_GET_PAGE:
> + pfn = gfn_to_pfn(vcpu->kvm, op.u.gen.pfn);
> + page = pfn_to_page(pfn);
> + oid.oid[0] = op.u.gen.oid[0];
> + oid.oid[1] = op.u.gen.oid[1];
> + oid.oid[2] = op.u.gen.oid[2];
> + *ret = zcache_get_page(TMEM_CLI, op.pool_id,
> + &oid, op.u.gen.index, page);
> + break;
> + case TMEM_FLUSH_PAGE:
> + oid.oid[0] = op.u.gen.oid[0];
> + oid.oid[1] = op.u.gen.oid[1];
> + oid.oid[2] = op.u.gen.oid[2];
> + *ret = zcache_flush_page(op.u.gen.cli_id, op.pool_id,
> + &oid, op.u.gen.index);
> + break;
> + case TMEM_FLUSH_OBJECT:
> + oid.oid[0] = op.u.gen.oid[0];
> + oid.oid[1] = op.u.gen.oid[1];
> + oid.oid[2] = op.u.gen.oid[2];
> + *ret = zcache_flush_object(op.u.gen.cli_id, op.pool_id, &oid);
> + break;
> + }
> + return 0;
> +}
> +
> +/*
> * zcache initialization
> * NOTE FOR NOW zcache MUST BE PROVIDED AS A KERNEL BOOT PARAMETER OR
> * NOTHING HAPPENS!
> @@ -1934,10 +1993,19 @@ static int __init no_frontswap(char *s)
>
> __setup("nofrontswap", no_frontswap);
>
> +static int kvm_tmem_enabled = 0;
No need to declare it zero. Don't we want to have it running by default?
So the function below would be 'disable_kvm' instead of enabling it?
> +
> +static int __init enable_kvm_tmem(char *s)
> +{
> + kvm_tmem_enabled = 1;
> + return 1;
> +}
> +
> +__setup("kvmtmem", enable_kvm_tmem);
> +
> static int __init zcache_init(void)
> {
> int ret = 0;
> -
> #ifdef CONFIG_SYSFS
> ret = sysfs_create_group(mm_kobj, &zcache_attr_group);
> if (ret) {
> @@ -1946,7 +2014,7 @@ static int __init zcache_init(void)
> }
> #endif /* CONFIG_SYSFS */
> #if defined(CONFIG_CLEANCACHE) || defined(CONFIG_FRONTSWAP)
> - if (zcache_enabled) {
> + if (zcache_enabled || kvm_tmem_enabled) {
> unsigned int cpu;
>
> tmem_register_hostops(&zcache_hostops);
> @@ -1966,11 +2034,25 @@ static int __init zcache_init(void)
> sizeof(struct tmem_objnode), 0, 0, NULL);
> zcache_obj_cache = kmem_cache_create("zcache_obj",
> sizeof(struct tmem_obj), 0, 0, NULL);
> - ret = zcache_new_client(LOCAL_CLIENT);
> - if (ret) {
> - pr_err("zcache: can't create client\n");
> + if(kvm_tmem_enabled) {
Space..
> + ret = zcache_new_client(TMEM_CLI);
> + if(ret) {
> + pr_err("zcache: can't create client\n");
> + goto out;
> + }
> + zbud_init();
> + register_shrinker(&zcache_shrinker);
> + pr_info("zcache: transcendent memory enabled using kernel "
> + "for kvm guests\n");
> goto out;
> }
> + else {
> + ret = zcache_new_client(LOCAL_CLIENT);
> + if (ret) {
> + pr_err("zcache: can't create client\n");
> + goto out;
> + }
> + }
> #endif
> #ifdef CONFIG_CLEANCACHE
> if (zcache_enabled && use_cleancache) {
>
--
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