| Message ID | 1452688338-70075-6-git-send-email-roger.pau@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
>>> On 13.01.16 at 13:32, <roger.pau@citrix.com> wrote: > Only intercept accesses to IO port 0xcf8 if there's at least one IOREQ > server, otherwise it makes no sense since the only code that uses the value > stored by hvm_access_cf8 is the IOREQ server. Afaict an ioreq server could also attach subsequently - Paul? Jan
On 13/01/16 16:38, Jan Beulich wrote: >>>> On 13.01.16 at 13:32, <roger.pau@citrix.com> wrote: >> Only intercept accesses to IO port 0xcf8 if there's at least one IOREQ >> server, otherwise it makes no sense since the only code that uses the value >> stored by hvm_access_cf8 is the IOREQ server. > Afaict an ioreq server could also attach subsequently - Paul? Indeed it can. The last-latched cfc/cf8 values should be accurate at that point. The intercept needs to stay. ~Andrew
> -----Original Message----- > From: Jan Beulich [mailto:JBeulich@suse.com] > Sent: 13 January 2016 16:39 > To: Paul Durrant; Roger Pau Monne > Cc: Andrew Cooper; xen-devel@lists.xenproject.org > Subject: Re: [PATCH 5/5] x86/HVM: don't setup an intercept handler for IO > port 0xcf8 unconditionally > > >>> On 13.01.16 at 13:32, <roger.pau@citrix.com> wrote: > > Only intercept accesses to IO port 0xcf8 if there's at least one IOREQ > > server, otherwise it makes no sense since the only code that uses the value > > stored by hvm_access_cf8 is the IOREQ server. > > Afaict an ioreq server could also attach subsequently - Paul? > Indeed, ioreq servers can come and go at any time. Paul > Jan
El 13/01/16 a les 17.48, Paul Durrant ha escrit: >> -----Original Message----- >> From: Jan Beulich [mailto:JBeulich@suse.com] >> Sent: 13 January 2016 16:39 >> To: Paul Durrant; Roger Pau Monne >> Cc: Andrew Cooper; xen-devel@lists.xenproject.org >> Subject: Re: [PATCH 5/5] x86/HVM: don't setup an intercept handler for IO >> port 0xcf8 unconditionally >> >>>>> On 13.01.16 at 13:32, <roger.pau@citrix.com> wrote: >>> Only intercept accesses to IO port 0xcf8 if there's at least one IOREQ >>> server, otherwise it makes no sense since the only code that uses the value >>> stored by hvm_access_cf8 is the IOREQ server. >> >> Afaict an ioreq server could also attach subsequently - Paul? >> > > Indeed, ioreq servers can come and go at any time. Right, then I will have to prevent hvm_access_cf8 from being added if the domain is the hardware domain, otherwise it overlaps with the Dom0 passthrough intercept (handle_pvh_io). Roger.
>>> On 14.01.16 at 09:35, <roger.pau@citrix.com> wrote: > El 13/01/16 a les 17.48, Paul Durrant ha escrit: >>> -----Original Message----- >>> From: Jan Beulich [mailto:JBeulich@suse.com] >>> Sent: 13 January 2016 16:39 >>> To: Paul Durrant; Roger Pau Monne >>> Cc: Andrew Cooper; xen-devel@lists.xenproject.org >>> Subject: Re: [PATCH 5/5] x86/HVM: don't setup an intercept handler for IO >>> port 0xcf8 unconditionally >>> >>>>>> On 13.01.16 at 13:32, <roger.pau@citrix.com> wrote: >>>> Only intercept accesses to IO port 0xcf8 if there's at least one IOREQ >>>> server, otherwise it makes no sense since the only code that uses the value >>>> stored by hvm_access_cf8 is the IOREQ server. >>> >>> Afaict an ioreq server could also attach subsequently - Paul? >>> >> >> Indeed, ioreq servers can come and go at any time. > > Right, then I will have to prevent hvm_access_cf8 from being added if > the domain is the hardware domain, otherwise it overlaps with the Dom0 > passthrough intercept (handle_pvh_io). Yes, that indeed makes sense. Jan
On 14/01/16 09:12, Jan Beulich wrote: >>>> On 14.01.16 at 09:35, <roger.pau@citrix.com> wrote: >> El 13/01/16 a les 17.48, Paul Durrant ha escrit: >>>> -----Original Message----- >>>> From: Jan Beulich [mailto:JBeulich@suse.com] >>>> Sent: 13 January 2016 16:39 >>>> To: Paul Durrant; Roger Pau Monne >>>> Cc: Andrew Cooper; xen-devel@lists.xenproject.org >>>> Subject: Re: [PATCH 5/5] x86/HVM: don't setup an intercept handler for IO >>>> port 0xcf8 unconditionally >>>> >>>>>>> On 13.01.16 at 13:32, <roger.pau@citrix.com> wrote: >>>>> Only intercept accesses to IO port 0xcf8 if there's at least one IOREQ >>>>> server, otherwise it makes no sense since the only code that uses the value >>>>> stored by hvm_access_cf8 is the IOREQ server. >>>> Afaict an ioreq server could also attach subsequently - Paul? >>>> >>> Indeed, ioreq servers can come and go at any time. >> Right, then I will have to prevent hvm_access_cf8 from being added if >> the domain is the hardware domain, otherwise it overlaps with the Dom0 >> passthrough intercept (handle_pvh_io). > Yes, that indeed makes sense. Even for the hardware domain, cf8 needs trapping and emulating (although on a different path). Being an indirect port pair shared by Xen and dom0, dom0 cannot use it directly of its own accord. ~Andrew
El 14/01/16 a les 11.50, Andrew Cooper ha escrit: > On 14/01/16 09:12, Jan Beulich wrote: >>>>> On 14.01.16 at 09:35, <roger.pau@citrix.com> wrote: >>> El 13/01/16 a les 17.48, Paul Durrant ha escrit: >>>>> -----Original Message----- >>>>> From: Jan Beulich [mailto:JBeulich@suse.com] >>>>> Sent: 13 January 2016 16:39 >>>>> To: Paul Durrant; Roger Pau Monne >>>>> Cc: Andrew Cooper; xen-devel@lists.xenproject.org >>>>> Subject: Re: [PATCH 5/5] x86/HVM: don't setup an intercept handler for IO >>>>> port 0xcf8 unconditionally >>>>> >>>>>>>> On 13.01.16 at 13:32, <roger.pau@citrix.com> wrote: >>>>>> Only intercept accesses to IO port 0xcf8 if there's at least one IOREQ >>>>>> server, otherwise it makes no sense since the only code that uses the value >>>>>> stored by hvm_access_cf8 is the IOREQ server. >>>>> Afaict an ioreq server could also attach subsequently - Paul? >>>>> >>>> Indeed, ioreq servers can come and go at any time. >>> Right, then I will have to prevent hvm_access_cf8 from being added if >>> the domain is the hardware domain, otherwise it overlaps with the Dom0 >>> passthrough intercept (handle_pvh_io). >> Yes, that indeed makes sense. > > Even for the hardware domain, cf8 needs trapping and emulating (although > on a different path). Being an indirect port pair shared by Xen and > dom0, dom0 cannot use it directly of its own accord. Sure, but it has to be handled by handle_pvh_io (which I plan to rename in due time) and not hvm_access_cf8. Roger.
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c index 28c6cd9..24c3d46 100644 --- a/xen/arch/x86/hvm/hvm.c +++ b/xen/arch/x86/hvm/hvm.c @@ -1141,6 +1141,13 @@ static int hvm_create_ioreq_server(struct domain *d, domid_t domid, if ( rc ) goto fail3; + /* + * We cannot fail after this point, or we risk registering the handler + * multiple times (there's no unregister function yet). + */ + if ( list_empty(&d->arch.hvm_domain.ioreq_server.list) ) + register_portio_handler(d, 0xcf8, 4, hvm_access_cf8); + list_add(&s->list_entry, &d->arch.hvm_domain.ioreq_server.list); @@ -1625,7 +1632,6 @@ int hvm_domain_initialise(struct domain *d) pit_init(d, cpu_khz); register_portio_handler(d, 0xe9, 1, hvm_print_line); - register_portio_handler(d, 0xcf8, 4, hvm_access_cf8); rc = hvm_funcs.domain_initialise(d); if ( rc != 0 )
Only intercept accesses to IO port 0xcf8 if there's at least one IOREQ server, otherwise it makes no sense since the only code that uses the value stored by hvm_access_cf8 is the IOREQ server. Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> --- Cc: Jan Beulich <jbeulich@suse.com> Cc: Andrew Cooper <andrew.cooper3@citrix.com> --- xen/arch/x86/hvm/hvm.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)