Commit bb2baeb2 authored by Mingwei Zhang's avatar Mingwei Zhang Committed by Paolo Bonzini
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KVM: SVM: improve the code readability for ASID management 



KVM SEV code uses bitmaps to manage ASID states. ASID 0 was always skipped
because it is never used by VM. Thus, in existing code, ASID value and its
bitmap postion always has an 'offset-by-1' relationship.

Both SEV and SEV-ES shares the ASID space, thus KVM uses a dynamic range
[min_asid, max_asid] to handle SEV and SEV-ES ASIDs separately.

Existing code mixes the usage of ASID value and its bitmap position by
using the same variable called 'min_asid'.

Fix the min_asid usage: ensure that its usage is consistent with its name;
allocate extra size for ASID 0 to ensure that each ASID has the same value
with its bitmap position. Add comments on ASID bitmap allocation to clarify
the size change.

Signed-off-by: default avatarMingwei Zhang <mizhang@google.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Marc Orr <marcorr@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Alper Gun <alpergun@google.com>
Cc: Dionna Glaze <dionnaglaze@google.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Vipin Sharma <vipinsh@google.com>
Cc: Peter Gonda <pgonda@google.com>
Cc: Joerg Roedel <joro@8bytes.org>
Message-Id: <20210802180903.159381-1-mizhang@google.com>
[Fix up sev_asid_free to also index by ASID, as suggested by Sean
 Christopherson, and use nr_asids in sev_cpu_init. - Paolo]
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 179c6c27

arch/x86/kvm/svm/sev.c

+24 −19
Original line number Diff line number Diff line
@@ -64,6 +64,7 @@ static DEFINE_MUTEX(sev_bitmap_lock); 
unsigned int max_sev_asid;

static unsigned int min_sev_asid;

static unsigned long sev_me_mask;

static unsigned int nr_asids;

static unsigned long *sev_asid_bitmap;

static unsigned long *sev_reclaim_asid_bitmap;
@@ -78,11 +79,11 @@ struct enc_region { 
/* Called with the sev_bitmap_lock held, or on shutdown  */

static int sev_flush_asids(int min_asid, int max_asid)

{

	int ret, pos, error = 0;

	int ret, asid, error = 0;



	/* Check if there are any ASIDs to reclaim before performing a flush */

	pos = find_next_bit(sev_reclaim_asid_bitmap, max_asid, min_asid);

	if (pos >= max_asid)

	asid = find_next_bit(sev_reclaim_asid_bitmap, nr_asids, min_asid);

	if (asid > max_asid)

		return -EBUSY;



	/*
@@ -115,15 +116,15 @@ static bool __sev_recycle_asids(int min_asid, int max_asid) 


	/* The flush process will flush all reclaimable SEV and SEV-ES ASIDs */

	bitmap_xor(sev_asid_bitmap, sev_asid_bitmap, sev_reclaim_asid_bitmap,

		   max_sev_asid);

	bitmap_zero(sev_reclaim_asid_bitmap, max_sev_asid);

		   nr_asids);

	bitmap_zero(sev_reclaim_asid_bitmap, nr_asids);



	return true;

}



static int sev_asid_new(struct kvm_sev_info *sev)

{

	int pos, min_asid, max_asid, ret;

	int asid, min_asid, max_asid, ret;

	bool retry = true;

	enum misc_res_type type;
@@ -143,11 +144,11 @@ static int sev_asid_new(struct kvm_sev_info *sev) 
	 * SEV-enabled guests must use asid from min_sev_asid to max_sev_asid.

	 * SEV-ES-enabled guest can use from 1 to min_sev_asid - 1.

	 */

	min_asid = sev->es_active ? 0 : min_sev_asid - 1;

	min_asid = sev->es_active ? 1 : min_sev_asid;

	max_asid = sev->es_active ? min_sev_asid - 1 : max_sev_asid;

again:

	pos = find_next_zero_bit(sev_asid_bitmap, max_sev_asid, min_asid);

	if (pos >= max_asid) {

	asid = find_next_zero_bit(sev_asid_bitmap, max_asid + 1, min_asid);

	if (asid > max_asid) {

		if (retry && __sev_recycle_asids(min_asid, max_asid)) {

			retry = false;

			goto again;
@@ -157,11 +158,11 @@ static int sev_asid_new(struct kvm_sev_info *sev) 
		goto e_uncharge;

	}



	__set_bit(pos, sev_asid_bitmap);

	__set_bit(asid, sev_asid_bitmap);



	mutex_unlock(&sev_bitmap_lock);



	return pos + 1;

	return asid;

e_uncharge:

	misc_cg_uncharge(type, sev->misc_cg, 1);

	put_misc_cg(sev->misc_cg);
@@ -179,13 +180,12 @@ static int sev_get_asid(struct kvm *kvm) 
static void sev_asid_free(struct kvm_sev_info *sev)

{

	struct svm_cpu_data *sd;

	int cpu, pos;

	int cpu;

	enum misc_res_type type;



	mutex_lock(&sev_bitmap_lock);



	pos = sev->asid - 1;

	__set_bit(pos, sev_reclaim_asid_bitmap);

	__set_bit(sev->asid, sev_reclaim_asid_bitmap);



	for_each_possible_cpu(cpu) {

		sd = per_cpu(svm_data, cpu);
@@ -1857,12 +1857,17 @@ void __init sev_hardware_setup(void) 
	min_sev_asid = edx;

	sev_me_mask = 1UL << (ebx & 0x3f);



	/* Initialize SEV ASID bitmaps */

	sev_asid_bitmap = bitmap_zalloc(max_sev_asid, GFP_KERNEL);

	/*

	 * Initialize SEV ASID bitmaps. Allocate space for ASID 0 in the bitmap,

	 * even though it's never used, so that the bitmap is indexed by the

	 * actual ASID.

	 */

	nr_asids = max_sev_asid + 1;

	sev_asid_bitmap = bitmap_zalloc(nr_asids, GFP_KERNEL);

	if (!sev_asid_bitmap)

		goto out;



	sev_reclaim_asid_bitmap = bitmap_zalloc(max_sev_asid, GFP_KERNEL);

	sev_reclaim_asid_bitmap = bitmap_zalloc(nr_asids, GFP_KERNEL);

	if (!sev_reclaim_asid_bitmap) {

		bitmap_free(sev_asid_bitmap);

		sev_asid_bitmap = NULL;
@@ -1907,7 +1912,7 @@ void sev_hardware_teardown(void) 
		return;



	/* No need to take sev_bitmap_lock, all VMs have been destroyed. */

	sev_flush_asids(0, max_sev_asid);

	sev_flush_asids(1, max_sev_asid);



	bitmap_free(sev_asid_bitmap);

	bitmap_free(sev_reclaim_asid_bitmap);
@@ -1921,7 +1926,7 @@ int sev_cpu_init(struct svm_cpu_data *sd) 
	if (!sev_enabled)

		return 0;



	sd->sev_vmcbs = kcalloc(max_sev_asid + 1, sizeof(void *), GFP_KERNEL);

	sd->sev_vmcbs = kcalloc(nr_asids, sizeof(void *), GFP_KERNEL);

	if (!sd->sev_vmcbs)

		return -ENOMEM;