| Message ID | 20210412105243.23354-4-luca.fancellu@arm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | xen/arm: Prevent Dom0 to be loaded when using dom0less | expand |
Hi Luca, The title probably wants to be updated as you don't really reserve domid 0. How about: xen/arm: Clarify how the domid is decided in create_domUs() On 12/04/2021 11:52, Luca Fancellu wrote: > This patch adds a comment in create_domUs() right before > domain_create() to explain the importance of the pre-increment > operator on the variable max_init_domid, to ensure that the > domid 0 is allocated only during start_xen() function by the > create_dom0() and not on any other possible code path to the > domain_create() function. > > Signed-off-by: Luca Fancellu <luca.fancellu@arm.com> > --- > Changes in v3: > - removed check introduced in v2. > --- > xen/arch/arm/domain_build.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c > index 359957dc1b..b1d7b9849f 100644 > --- a/xen/arch/arm/domain_build.c > +++ b/xen/arch/arm/domain_build.c > @@ -2508,6 +2508,11 @@ void __init create_domUs(void) > GUEST_VPL011_SPI - 32 + 1); > } > > + /* > + * The variable max_init_domid is initialized with zero, so here it's > + * very important to use the pre-increment operator to call > + * domain_create() with a domid > 0. (domid == 0 is reserved for Dom0) > + */ > d = domain_create(++max_init_domid, &d_cfg, false); > if ( IS_ERR(d) ) > panic("Error creating domain %s\n", dt_node_name(node)); >
> On 13 Apr 2021, at 18:00, Julien Grall <julien@xen.org> wrote: > > Hi Luca, > > The title probably wants to be updated as you don't really reserve domid 0. How about: > > xen/arm: Clarify how the domid is decided in create_domUs() Sure I’ll update in the v4 patch I will send soon Cheers, Luca > > On 12/04/2021 11:52, Luca Fancellu wrote: >> This patch adds a comment in create_domUs() right before >> domain_create() to explain the importance of the pre-increment >> operator on the variable max_init_domid, to ensure that the >> domid 0 is allocated only during start_xen() function by the >> create_dom0() and not on any other possible code path to the >> domain_create() function. >> Signed-off-by: Luca Fancellu <luca.fancellu@arm.com> >> --- >> Changes in v3: >> - removed check introduced in v2. >> --- >> xen/arch/arm/domain_build.c | 5 +++++ >> 1 file changed, 5 insertions(+) >> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c >> index 359957dc1b..b1d7b9849f 100644 >> --- a/xen/arch/arm/domain_build.c >> +++ b/xen/arch/arm/domain_build.c >> @@ -2508,6 +2508,11 @@ void __init create_domUs(void) >> GUEST_VPL011_SPI - 32 + 1); >> } >> + /* >> + * The variable max_init_domid is initialized with zero, so here it's >> + * very important to use the pre-increment operator to call >> + * domain_create() with a domid > 0. (domid == 0 is reserved for Dom0) >> + */ >> d = domain_create(++max_init_domid, &d_cfg, false); >> if ( IS_ERR(d) ) >> panic("Error creating domain %s\n", dt_node_name(node)); > > -- > Julien Grall
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c index 359957dc1b..b1d7b9849f 100644 --- a/xen/arch/arm/domain_build.c +++ b/xen/arch/arm/domain_build.c @@ -2508,6 +2508,11 @@ void __init create_domUs(void) GUEST_VPL011_SPI - 32 + 1); } + /* + * The variable max_init_domid is initialized with zero, so here it's + * very important to use the pre-increment operator to call + * domain_create() with a domid > 0. (domid == 0 is reserved for Dom0) + */ d = domain_create(++max_init_domid, &d_cfg, false); if ( IS_ERR(d) ) panic("Error creating domain %s\n", dt_node_name(node));
This patch adds a comment in create_domUs() right before domain_create() to explain the importance of the pre-increment operator on the variable max_init_domid, to ensure that the domid 0 is allocated only during start_xen() function by the create_dom0() and not on any other possible code path to the domain_create() function. Signed-off-by: Luca Fancellu <luca.fancellu@arm.com> --- Changes in v3: - removed check introduced in v2. --- xen/arch/arm/domain_build.c | 5 +++++ 1 file changed, 5 insertions(+)